Sensory, Attentional And Perceptual Processes – Notes for Class 11 Psychology
• We know our environment in particular and the world at large through our sense organs. The information collected by our sense organs is basis of our cognition. The whole phenomena of cognitive functioning is determined by sensation, attention and perception. Sensation refers to the stimulation of a receptor (e.g., eyes) rather than the experience (e.g., seeing i.e. perception). Attention refers to the tendency of an organism to focus on selected features of the environment. Perception is a process by which information in the environment is transformed into an experience.
I. External stimuli are received through specialized sensory receptor cells. (A) Sense organs receive stimuli, convert sensory energy into neural impulses, and send neural messages to the brain for interpretation. (B) Psychophysics is the field of psychology that studies the relationships between physical stimuli and psychological sensations and perceptions. II. The sense organs of sight transduce light energy. (A) The intensity of light waves largely determines brightness, while the wavelength (frequency) largely determines colour. (B) The eye, working much like a camera, is the primary sense organ for seeing. 1. Light enters the eye through the cornea (with the iris regulating the size of the pupil) and the lens into the retina. 2. Rods and cdnes convert light waves into neural impulses for transportation to the brain. 3. The 125 million rods, located throughout the retina except for the fovea, are active in peripheral vision and vision in dim light, but they do not play a role in colour vision. 4. The 6 million cones clustered mostly near the fovea code information for colour. 5. Both trichromatic theory and opponent-process theory are helpful in understanding colour vision. III. The sense of hearing detects sound waves. (A) The frequency of sound waves determines pitch, while the intensity determines loudness. (B) The ear is the primary sense organ for hearing. (C) Sound waves vibrate the eardrum, which is connected to a series of three movable bones (hammer, anvil, stirrup) in the midDiffemtial thresholde ear. (D) The inner ear, containing the cochlea and the organ of Corti, transduces the sound wave energy into neural impulses for transportation to the brain. IV. Chemical senses respond to chemicals rather than to energy in the environment. (A) In the sense of taste, chemicals produce the perception of qualities of sweet, sour, bitter, and salty. (B) In the sense of smell, chemicals produce the perception of odours. V. Internal stimuli are also received by the sensory system. (A) The vestibular organ provides information about body orientation, while the kinesthetic sense reports bodily position and movement. (B) The various skin senses can detect pressure, temperature, and pain. 1. Two sensations of pain reach the brain at slightly different times because they travel on different neural pathways. (a) The first sensation reaches the somatosensory area quickly on myelinated neurons. (b) The more emotional type of pain reaches the limbic system more slowly on unmyelinated neurons.
Word That Matter
1. Absolute threshold : The minimum intensity necessary for a stimulus to be detected. 2. After images : A visual image that persists after a stimulus is removed. 3. Binocular cues : Depth cues, such as retinal disparity and convergence, that depend on the use of two eyes. 4. Bottom-up processing : In form perception, progression from individual elements to the whole. 5. Cochlea : The fluid-filled, coiled tunnel in the inner ear that contains the receptors for hearing. 6. Cones : Specialised visual receptors that play a key role in daylight vision and colour vision. 7. Dark adaptation : The process in which the eyes become more sensitive to light in low illumination. 8. Depth perception : The perception of the distance of an object from the observer or the distance from front to back of a solid object. 9. Difference threshold : The minimum difference between a pair of stimuli that can be perceived. 10. Divided attention : The process by which attention is split between two or more sets of stimuli. 11. Eustachian tube : Passage that connects the middle ear to the throat and allows release of pressure. 12. Gestalt: An organized whole, Gestalt psychologists emphasise our tendency to integrate pieces of information into meaningful wholes. 13. Lightadaptationr : Theadjustmentoftherodsandconesintheeyeto changes in illumination. 14. Loudness : The perception of a sound wave’s amplitude. 15. Monocular cues : Visual cues from one eye only. 16. Organ of corti : Structure on the surface of the basilar membrane that contains the receptor cells for hearing. 17. Perceptual constancy : The ability, in perception, to draw similar inferences about the world from different patterns of sensory activity (e.g., a person seen from many different angles is still perceived as the same person). 18. Phi phenomenon : The illusion of movement created by presenting visual stimuli in rapid succession. 19. Pitch : The perceptual interpretation of a sound’s frequency. 20. Primary colours: A set of three colours, i.e. red, green, and blue, when mixed in unequal amounts can produce any colour. 21. Retina: Layer of cells at the back of the eye containing photoreceptors. 22. Rods : Specialised visual receptors that play a key role in night vision and peripheral vision. 23. Selective attention : The focusing of conscious awareness on a particular stimulus. 24. Timbre : The characteristic quality of a tone produced by the combination of overtones heard along with the pure tone. 25. Top-down processing : In form perception, a progression from the whole to the elements. 26. Visual illusions: Physical stimuli that consistently produce errors in perception. 27. Wavelength: The distance from the peak of one light or sound wave to the peak of the next.
• Development is viewed as lifelong, multidimensional, multidirectional, plastic, historically embedded, multidisciplinary and biological. Cognitive and socio-emotional processes influence development. • The ideas about development revolve around three issues: nature and nurture, continuity and discontinuity and stability and change. Some basic principles underline the process of development, which can be observed in all human beings. • There are differentrstages of development signifying specific developmental tasks to be accomplished during that period or stage of life. • Infancy is the period from birth to 18 months of age. It marks the beginning of language, symbolic thought, sensorimotor coordination and social learning. • Early childhood years extend from end of infancy to 5 to 6 years of age and are also called the “preschool year”. The middle and late childhood years is the period from 6 to 11 years of age. The child is able to master the fundamental skills of reading, writing and arithmetic, the child also develops physically, socially and morally. • Adolescence begins at puberty, and is the transition from childhood to adulthood. Physical changes in adolescence include the development of secondary sex characteristics, hormonal changes, and spurt in growth. The major developmental tasks for the adolescent include identity formation and coming to terms with biological changes taking place. • Adult year is the time of establishing personal and economic independence, starting a career, getting married and starting a family. Middle adulthood is the time for the individual to adjust to vocational changes, expanding families, changing roles e.g. grand-parenting etc. Old age is the time to respond to changes in physical and cognitive capacities, retirement and death of spouse. • Later adult years represent another segment of life span which are accompanied by physiological and cognitive changes. • The chapter gives an overview of the entire lifespan, from birth to death. You must have realized that development and change continue throughout the life span. No period of life is completely stable or unchanging. If one aspect has stabilized others are . developing. Infact the human being is constantly making adaptation to the changing world throughout his/her life. Word That Matter 1. Adolescence: The developmental period of transition from childhood to early adulthood, starting at approximately 11 to 13 years of age and ending at 18 to 20 years of age. 2. Animism : A facet of preoperational thought; the belief that inanimate objects have “lifelike” qualities and are capable of action. 3. Attachment: A close emotional bond between the infant and the parents or caregiver. 4. Centration: The focusing or centring of attention on one characteristic to the exclusion of all others. 5. Cephalocaudal pattern : The sequence in which the greatest growth occurs at the top- the head with physical growth in size, weight, and feature differentiation gradually working from top to bottom. 6. Concrete operational stage : The third piagetian stage, lasting approximately from 7 to 11 years. 7. Deductive reasoning: Reaching a conclusion by accepting the premises of an argument and then following the formal logical rules. 8. Development : It is the pattern of progressive, orderly, and predictable changes that begin at conception and continue throughout life. 9. Egocentrism : A salient feature of pre-operational thought, which refers to the inability to distinguish between one’s own perspective and someone else’s perspective. 10. Evolution: The theory proposed by Charles Darwin that over time organisms originate and change in response to adaptational demands of their unique environments. 11. Gender: The social dimension of being male or female. 12. Maturation : The orderly sequence of changes dictated by each person’s genetic blueprint. 13. Menarche : The first occurrence of menstruation. 14. Motor development: The progression of muscular coordination required for physical activities. 15. Object permanence: Understanding that objects and events continue to exist even when they cannot directly be seen, heard, or touched. 16. Operations : Internalised sets of actions that allow the child to do mentally what was done physically before. ‘ 17. Phenotype : Observable features by which individuals are recognised. 18. Prenatal period : The time from conception to birth. 19. Pre-operational stage : The second Piagetian stage in which children begin to represent world with words, images, and drawings but cannot perform operations in logical manner. 20. Primary sex characteristics : The sexual structures necessary for reproduction. 21. Proximodistal trend: The center-outward direction of motor development. 22. Puberty : A period of rapid skeletal and sexual maturation that occurs mainly in early adolescence. 23. Reflex arc : A receptor neuron and an efferent neuron capable of mediating a S-R sequence. 24. Secondary sex characteristics : Physical features that are associated with gender but that are not directly involved in reproduction. 25. Self : The individuals perception or awareness of herself or himself-of her or his body, abilities, personality traits, and ways of doing things. 26. Sensorimotor stage: The first Piagetian stage in which infants construct an understanding of the world by coordinating sensory experiences with physical and motor actions.
Let’s begin with the first topic for The Bases of Human Behaviour Class 11 notes, neurons and how they transmit information.
Neurons are the basic unit of our nervous system and these are specialized cells that convert various forms of stimuli into electrical impulses.
They receive information from sense organs or adjacent neurons and transfer them to the central nervous system(CNS) and bring motor information from the central nervous system to the motor neurons
Pathway of how neurons transmit information is illustrated below-
Structure Of Neuron
Here is the structure of a Neuron as per Class 11 Bases of Human Behaviour:
Dendrites receive the incoming neural impulses from adjacent neurons or directly from sense organs.
Then the nerve impulse is passed on to the main body of the neuron which is the soma
From there it is passed on the axon.
Axon mainly helps in transmitting the information to the terminal buttons.
The main function of terminal buttons is to transmit the information to another neuron, gland, or muscle.
Neurons generally conduct information in one direction, which is from dendrites through soma and axon to terminal buttons.
Nervous System
The next topic for Bases of Human Behaviour Class 11 notes is the nervous system. The human nervous system is the most complex and developed part of all living creatures and is a massive network of nerve cells that relays messages to and from the CNS. Its schematic representation is depicted below for ease of clarity and understanding:
The central nervous system is the part of the brain which is found inside the hard bony cases ( cranium and backbone) is classified as CNS. The brain and Spinal Cord are the organs of this system.
The parts of the nervous system other than the central nervous system are placed in the Peripheral Nervous System(PNS) which is further classified into the somatic nervous system and autonomic nervous system.
The PNS comprises all the neurons and nerve fibers that facilitate the connection of CNS to the rest of the body and provides information to the CNS from sensory receptors (eyes, skin) and relays back motor commands from the brain to muscles and glands
Somatic Nervous System is concerned with voluntary actions and consists of two nerves:
– Sensory nerves that carries information from sense organs to central nervous system.
– Motor nerves that carries information from central nervous system to sense organs.
The autonomic nervous system governs those activities which are not under the direct control of humans and activities governed by it are blood circulation, breathing, emotional reactions, etc.
The autonomic nervous system is further classified into:
Parasympathetic Division
Inhibits salivation
Increases sweating
Decreases digestive functions of the intestine
Accelerates heart
Sympathetic Division
Increases digestive functions of the intestine
Slows heart rate
Increases salivation
Inhibits sweating
The central nervous system is the center of all neural activity and it integrates all incoming sensory information performs all kinds of cognitive activities and issues motor commands to muscle and glands.
The central nervous system mainly consists of the brain and spinal cord.
The brain has 3 sections: The hindbrain, The Forebrain and the Midbrain.
The hindbrain consists of the medulla, pons, and cerebellum.
Medulla is responsible for regulation of heart rate,blood pressure,pons help in controlling respiration and cerebellum helps in coordinating voluntary muscle movement and maintaining body posture.
The forebrain consists of the cerebrum, the thalamus, and the hypothalamus.
Cerebrum consists of four lobes, mainly frontal lobe, parietal lobe, occipital lobe and temporal lobe. thalamus involves recognition of sensory stimuli and relay of sensory impulses to the cerebral cortex. The Hypothalamus is mainly responsible for regulating cardiac functioning,blood pressure and respiration.
The Midbrain is the major pathway of sensory and motor impulses moving between the forebrain and the midbrain. It is also responsible for the coordination of visual and auditory reflexes.
The spinal cord functions primarily in the transmission of neural signals between the brain and the rest of the body.
Its major functions are explained as follows:
Carries sensory impulses coming from lower parts of the body to the brain and motor impulses originating from the brain to all over the body
Performs some simple reflexes that do not involve the brain.
Reflex action is an involuntary action that occurs very quickly after its specific kind of stimulation without the conscious decision of the brain. For example, the eye blinking reflex.
The Endocrine System
Let’s read the details about the Endocrine system for the Bases of Human Behaviour Class 11 notes. The endocrine system comprises those glands that secrete hormones directly into the bloodstream and that helps in our development and behavior.
Heredity: Genes And Behavior
The next topic covered in our Bases of Human Behaviour Class 11 notes is Heredity.
The study of the inheritance of physical and psychological characteristics from ancestors is termed Genetics.
Chromosomes are hereditary elements of the body and they are threadlike paired structures in the nucleus of each cell. The number of chromosomes per nucleus is distinctive and is constant for each organism. Each chromosome consists of DNA and there are 23 pairs of chromosomes.
The genotype of an organism is the genetic code in its cells that influences an individual’s development whereas the phenotype depends on the genotype but can be influenced by environmental factors.
Genes are transmitted from parents to offspring whereas memes can be transmitted between any two individuals in a matter of hours.
Culture
Culture is another essential aspect under The Bases of Human Behavior Class 11 studies. It is the man-made part of the environment that comprises the diverse products of the behavior of many people including ourselves which can be material products, ideas, approaches, etc.
It comprises values that will be expressed and a language which will help in expressing values. It also contains a way of life that will be followed by the majority who grow up in that context
It includes behavioral products of others who preceded us
It indicates substantial or abstract particulars which have prior existence in one form or the other.
Acculturation And Enculturation
The next topic under The Bases of Human Behavior Class 11 is acculturation and enculturation.
Socialization
It is the process by which individuals acquire knowledge, skills, and dispositions that enable them to participate as effective group members and society. The features of socialization are as follows-
Forms the basis of social and cultural transmission from one generation to another.
Rewards and Punishments serve as the basic means of achieving the goals of socialization.
It involves deliberate teaching and engagement of people
The four main agents of socialization are Parents, School, Peer Groups, and Media Influences.
The description requires recording a particular behaviour and describing it accurately so as to attain a comprehensive understanding of the same
For example, morning habits may have a diverse range of behaviours like reading positive literature, meditation, exercise, journaling etc.
Prediction
It is the second goal of psychological enquiry
Here we attempt to understand the relationship between the behaviour we are describing with the other types of behaviour.
Explanation
It is the third goal of psychological enquiry
It attempts to explain the causal factors of behaviour and attain an understanding of the conditions in which the behaviour occurs or not.
Control
It is the fourth goal of psychological inquiry
It focuses on three things
Making a particular behaviour happen
Reducing it
Enhancing it
Application
It is the fifth goal of psychological enquiry
focuses on bringing out a positive change in people’s lives
Steps in Conducting a Scientific Research
Conceptualizing a problem
It is the first step of conducting a scientific research
The researcher selects a topic for study which is done on basis of either review of past research, observations, personal experience
Identification of problem
It is the second step of scientific research
Development of a tentative statement about the topic takes place which is termed a hypothesis
For example, “ greater is the amount of time spent by children in playing violent video games, the greater is the degree of impatience and anger developed by them”
Collection of data
This step focuses on developing a research design or blueprint of the entire study.
Decisions are taken about the following
Participants in the study
Methods of study
Tools to be used in research
Procedure for data collection
Drawing conclusions
The next step of scientific research is to analyse data through statistical procedures
It can be achieved through measures of central tendency like mean, median, mode and graphical presentations like pie charts, bar diagram
Revising research conclusions
The researcher revises the whole study and the hypothesis being taken is analysed thoroughly to see whether it stands true or not
• Psychology is defined as a science which studies mental processes, experiences and behaviour in different contexts. In doing so, it uses methods of biological and social sciences to obtain data systematically. It makes sense of the data so that it can be organized as knowledge. • Mental process: (i) Mental processes are activities of the mind and brain, related to cognition. (ii) We use mental processes when we think or remember something, or solve a problem. (iii) However, these mental activities are -different from neural activities, though they are mutually overlapping processes. (iv) The mind emerges and evolves as our interactions and experiences in this world get dynamically organized in the form of a system which is responsible for the occurrence of various mental processes. (v) Mental processes include reasoning, learning, thinking, problem solving, perception, etc. • Experiences: Experiences can be defined as the learning acquired through everyday life situation. (i) Experiences are subjective in nature, different for every individual. (ii) We cannot directly observe or know someone’s experience. (iii) Only the experiencing person can be aware or conscious of his/her experiences. Thus, experiences are imbedded in our awareness or consciousness. (iv) Experiences are influenced by internal and external conditions of the experiences. (v) The nature of the experience can only be understood by analyzing a complex set of internal and external conditions. (vi) Experiences are important because most of our learning is based on experiences. • Behaviours: (i) Behaviours are responses or reactions we make or activities we engage in. Eg. One can feel the heart pounding before taking an examination. (ii) Some behaviours such as thinking may be simple or complex, short or enduring. (iii) On the other hand, some behaviours can be outwardly seen or sensed and are called overt, for example laughing. (iv) All behaviours can be explained on the basis of S-R (Stimulus Response Relations). Any behaviour, overt or covert, is associated with or triggered by a stimulus. (v) Both stimulus and response can be internal or external. (vi) The same stimulus can have different responses, due to the organism variable. It emphasises upon an individual’s uniqueness and variation that make him different from other. • Psychology as a discipline (i) It studies behaviour, experience and mental processes. (ii) It seeks to understand and explain how the mind works and how different mental processes result in different behaviours. (iii) When we observe others, our own point of view or ways of understanding the world influence our interpretations of their behaviours and experiences. (iv) Psychologists try to minimize such biases in their explanations of behaviour and experience in various ways. (v) Some do so by making their analysis scientific and objective. (vi) Others seek to explain behaviour from the point of view of those experiencing persons because they think that selectivity is a necessary aspect of human experience. – Neuroscience and computer science borrow principles continuously from psychology. There are fast developing brain imaging techniques like MRI, ECG, etc. which make it possible to study brain processes in real time, i.e, when they are actually taking place. – Psychology as hybrid science : Psychology is a hybrid science that draws its influence from both natural and social sciences. • As a natural science : (i) Modem Psychology has developed because of the application of the scientific method to study, psychological phenomenon. (ii) As a physical science, it emphasizes on data that is systematic and can be studied under controlled conditions. (iii) It is quantitative and requires analysis. (iv) It takes influences from both physics and biology and believes in the Hypothetico Deductive Model (HDM). (v) Every or any hypothesis can be accepted or rejected on the basis of factors available. The model suggests that scientific advancement can take place if you have a theory to explain a phenomenon. (vi) A hypothesis is a tentative solution to a problem that helps in guiding a research or a theory. (vii) Hypothesis has been successfully used for determining many theories related to learning and memory. For example, the way a child has been brought up in his family will shape his personality. • Conscious means to be alert and aware of something. We are aware of all the outside environment as well as of the processes taking place in ourselves. Thus we are aware of the diverse sensations, perceptions, memories and feelings that take place in ourselves. In waking consciousness, we perceive time, place and events as real, meaningful and familiar. • Psychology is a social science because it studies the behaviour of human beings in their social tests cultural context. • Psychology as a social science discipline focuses on humans as social beings. • It focuses on the individual and communities in relation to their social, cultural and physical environment. • If we go back in History Psychology was defined as the science of the Mind. The use of term mind was considered to be relevant since it represents all the mental phenomena such as perceiving, thinking, imagining, reasoning and so on. But, certain difficulties regarding the term mind, its nature and its relationship with the body continued to persist. • Due to many researches particularly in Neurology the term ‘mind’ has returned in Psychology. It is true that Mind and brain are different and mind cannot exist without brain. Recent studies in Neuro Science has proved that there is a relationship between Mind and Behaviour. These researches and neurological experiments proved that a person suffer from damage of some part of the brain but his mind had remained intact. • Popular notions about the discipline of Psychology should be understood. Psychology as a science explains patterns of beha viour which can be predicted and explains behaviour before the act occur common sense. Psychology is based on hindsight. Professional Psychologists are trained, affiliated to some institution. They attain educational and professional qualification and understand, predict and modify human behaviour by scientific methods. • The emergence of Psychology as a science of mental processes, behaviour and experiences can be attributed to certain important development in Physiology and Physics as well as to the efforts of William Wilhelm Wundt who established first Psychological laboratory in 1879. • The evolution of Psychology can be traced in the major schools of Psychological thoughts. • Structuralism: It was proposed by Wundt and he studied the structure of conscious experiences by introspection. • Introspection is a procedure in which individual or subjects in Psychological experiments are asked to describe their own mental processes or experiences scientifically in detail. • Functionalism: It was proposed by William James and Jonh Dewey. They studied the functions of concious experiences in how people deal with the environment using introspection method. It shows the adaptation of human behaviour according to their changing needs. • Gestalt Psychology: The school was proposed by Koffka, Kohler and Werthiemer. It focussed on human perception. According to Gestalt Psychology, the whole is greater than the sum of its parts. • Behaviourism: It was proposed by John Watson and Skinner. According to this, Psychology must focus on what is observable and verifiable. • Psychoanalysis: It was proposed by Dr Sigmund Freud. He focused on unconscious mind and childhood experiences. • Humanistic Perspective: It was a revolt against Psychoanalysis and Behaviourism proposed by Carl Rogers and Abraham Maslow. It stated that human strive to grow and unfold their inner potential. • Cognitive Perspective: It focuses on mental processes. It views human beings as actively constructing their mind through their exploration into the Physical and Social world. Piaget stated that children actively construct their own minds whereas Vygofsky suggested that the mind is a joint cultural construction and emerges as a result of interaction between children and adults. • The modem era of Human Psychology began in the department of Philosophy at Calcutta University where the first syllabus of experiment on Psychology was introduced and the first Psychology Laboratory was established in 1915. Calcutta University started the first department of Psychology in the year 1916 and another department of applied Psychology in 1938. It was greatly influenced by Dr N.N. Sengupta. • Psychology as a science is closely related to other sciences. Behaviour is closely related to Biological make up, the hereditary predisposition and his level of maturity. Physiology, embroyology genetics and biochemistry are relating knowledge with Psychological functioning of human beings. A large number of hospitals now employ Psychologists. • The roots of Psychology are found in Philosophy particularly with respect to methods of knowing. • Psychology is closely related to Economics, Political Science and Sociology. Psychology has provided knowledge related to micro level economic behaviour and consumer behaviour. Psychology provides understanding of voting behaviour, exercise of power, opinion polls etc. Sociology is positively related to Psychology, e.g., Psychology studies human behaviour whereas Sociology studies human behaviour in society, i.e., socio cultural context. • The information processing approach in cognitive Psychology, to explain memory and concept of Artificial intelligence is highly linked with computer sciences. • Psychological principles explain crime, criminal behaviour, how well a witness remembers a crime, etc. Accordingly Psychology is closely related to law and criminology. Similarly Psychology has close bonds with Mass Communication, Music and Fine Arts, Architecture and Engineering. • Psychology as a discipline not only provide understanding to the development of theoretical knowledge of human behaviour but it has close linkages across Psychological processes. Psychologists now a days employed to help in diverse activities in different domains of Professional activities including hospitals, educational settings, industrial organisations, training institutes, military and government organisations. • Psychology continuously provides knowledge and understanding of human behaviour in different domains. Some of the emerging perspectives are Evolutionary Psychology, Cultural Psychology and Positive Psychology. • Evolutionary Psychology is an approach in social and natural sciences that examines psychological structure from a modem evolutionary perspective. • It seeks to identify which human psychological traits are involved in adaptations—that is the functional products of natural selection or sexual selection. • The goal of research in evolutionary psychology is to discover and understand the design of the human mind. • It is a theoretical approach to Psychology that attempts to explain useful mental and psychological traits — such as memory, perception or language — as adaptations, i.e., as the functional products of natural selection. • The purpose of this approach is to bring the functional way of thinking about biological mechanism such as the immune system into the field of Psychology. • In short Evolutionary Psychology is focused on how evolution has shaped the mind and behaviour. • Cultural Psychology is the study of how psychological and behavioural tendencies are rooted in and embodied in culture. • It studies how mind and culture are inseparable and mutually constitute, i.e., people are shaped by culture and their culture is shaped by them. • Cultural Psychology is the study of the way cultural traditions and social practices, regulate, express and transform the human Psyche, resulting less in Psychic unity for hurrian kind than in ethnic divergences in mind, self and emotion (Richard Shweder). • Contemporary psychologists have shown increasing interest in understanding what makes life good and meaningful. This development is termed as positive psychology. • There are some themes which provides direction to research and application of Psychology are to develop principles of behaviour and mental processes, function of the attributes of persons and environment, causality of human behaviour, culturally constructed human behaviour and controlling and modifying the behaviour. • Psychology can be viewed in two fold perspective which are complementary to each other i.e. Basic Psychology and Applied Psychology. Basic Psychology provides theories through researchers whereas Applied Psychology is related to the category of application according to the needs of society. • Psychologists study a wide range of issues related to mental and behavioural functioning. Psychologists study how the biological system works and socio-cultural bases shapes human behaviour. Contemporary psychologists study these processes from a perspective of lifespan. The basic psychological processes are parts of a dynamic regulated system. All these processes are interconnected and together help the organism to adapt to environment and grow. Knowing the environment requires several mental processes, which together are called cognition. Psychologists study how information is used in thinking, reasoning, decision-making, communicating and solving problems. 1. Behaviour: Any covert or overt action/reaction a person or animal does that can be observed in some way. 2.Behaviourism: A school of thought that emphasises objectivity, observable behavioural responses, learning, and environmental determinants. 3. Cognition: All the mental activities associated with knowing; namely, perceiving, thinking, and remembering, etc. These are associated with processing, understanding, and communication information. 4.Cognitive economy: A term to denote maximum and efficient use of the capacity of long-term memory through organisation of concepts in a hierarchical network. 5.Consciousness: Awareness of the general condition of one’s mind, awareness of particular mental contents, or self-awareness. 6. Constructivism: Modern cognitive psychology views human beings as actively constructing their minds through their exploration into the physical and the social world. 7. Developmental Psychology: A branch of psychology which establishes the physical, social and psychological changes that occur at different ages and stages over a life-span, from conception to old age. 8.Functionalism / Functional fixedness: The tendency to think of thinks only in terms of their usual functions, impediments to problem solving. The school of psychology That emphasised the utilitarian, adaptive functions of the human mind or consciousness. 9. Gestalt: An organised whole, Gestalt psychologists emphasise our tendency to integrate pieces of information into meaningful wholes. 10. Gestalt psychology: A branch of psychology in which behaviour is viewed as an integrated whole, greater than the sum of its parts. 11. Humanistic approach: The approach to Psychology that emphasises the person, or the self, and personal growth land development. 12. Hue: Property of chromatic colours or name of the colours. 13. Introspection: The process of looking inward to one’s feeling and conscious experience. 14. Mind: Mind is a concept, which refers to unique set of individual’s sensations, perceptions, memories, thoughts, dreams, motives and emotional feelings. 15. Neuro psychology: It is the scientific study of behaviour and mental processes as function of brain activity and the nervous system. 16. Physiological psychology: A scientific study of human and animal behaviour based on the relationship of physiological processes like those of nervous system, hormones, sensory organs and the behavioural parameters. 17. Psychoanalysis: A method of psychotherapy in which the therapist attempts to bring repressed unconscious material into conscious. 18. Sociology: The systematic study of the biological basis for social behaviour. 19.Stimulus: Any well-defined element in the environment affecting the organism, which may lead to an overt or a covert response. 20.Structuralism: Associated with Wilhelm Wundt, the approach to psychology that seeks to understand the structure and operation of consciousness, or the human mind.
A map, on the other hand, is a simplified depiction of an entire or part of the earth on a piece of paper. 3D to 2D
The scale decreases because it cannot be drawn accurately
Symbols, colors and shades are used
Selective, symbolic and generalized representation of the entire, or a portion of the Earth՚s surface, on a plane at a low level
Sketch is without scale
Map with scale
Types of Maps
Cadastral Map: A large-scale map drawn on a scale of 1: 500 to 1: 4000 to show property boundaries, with each number designated a parcel of land.
Map series: A group of maps built on the same scale, style, and specifications for a country or region.
Projection-map: The system of transformation of a spherical surface to a flat surface.
Pay Scale: The ratio between the distance of two points on the map, the plan or photograph, and the actual distance between the same two points on the ground.
Sketch Map: A simplified map that draws freehand that fails to preserve the actual scale or orientation.
Map Making Essentials
Scale
Map projection
Map normalization
Map design
Map creation and production
Scale – The scale of a map determines the extent of information content and the degree of reality with which it can be depicted on the map
Map Projection – Simplified representation of 3D. Transformation of all sides-curved-geomorphic surface in one direction-conversion in directions, distances, areas and shapes
Map Normalization – Purpose – Relief, drainage, vegetation, settlements; Select and simplify information
Map Design – Selection of appropriate symbols, their shape and form, style of lettering, width of lines, selection of colors and shades, arrangement of various elements of map design within the map for map narrative
Map making and production – first drawn with pen and ink and printed mechanically and now by computer
History of Map Making
The oldest map was found in Mesopotamia, drawn on an earthen pillar that dated to 2,500 BC.
Greek and Arab geographers laid the foundation for modern cartography – Earth՚s periphery and geographic coordinates in map-making
Maps were drawn at various projections to obtain the correct direction, the correct distance, and to measure the area correctly.
19th & 20th Century – Aerial Photography + Exciting Map
Mapping in India – Vedic Period
In the classical treaties of Arya Bhatt, Varahamihir and Bhaskar, the expressions were crystallized into hant doctrines or laws.
7 biped by Indian scholars
Mahabharata imagines a round world surrounded by water
Sher Shah Suri՚s revenue maps further enriched the mapping techniques during the medieval period.
Todarmal pioneered land surveying and mapping for revenue collection
An intensive topographic survey for the preparation of an up-to-date map was taken with the establishment of the Survey of India in 1767, concluding in 1785 with a map of Hindustan.
Types of Maps Based on Scale
Large-scale maps are produced to show smaller areas at relatively larger scales.
Small-scale maps are drawn to show large areas.
Large-scale maps: Large-scale maps are divided into the following types: (a) cadastral maps (b) topographic maps
a) Cadastral Maps: The word ‘cadastral’ is derived from the French word ‘cadaster’ which means ‘register of territorial property’ . These maps are designed to show the ownership of land property by demarcation of arable land and the planning of individual houses in urban areas. Keeping records of ownership as well as realizing revenue and taxes. Village 1: 4000 and city 1: 2000
b) Topographic maps: These maps are also prepared on a large scale. Topographic maps are based on accurate surveys and are drawn as a series of maps created by the national mapping agencies of almost all countries of the world. Pay scale of 1: 250,000, 1: 50,000 and 1: 25,000 – relief, drainage, agricultural land, forests, settlements
Small Scale Maps: Contains wall and atlas maps
a) Wall maps: These maps are usually prepared on the basis of large size paper or plastic for use in classrooms or lecture halls. Atlas Map Scale < Wall Map Scale < Topographic Map
b) Atlas Maps: Atlas maps are very small scale maps. These maps represent large areas and provide highly generalized images of physical or cultural features.
Types of Maps Based on Function
physical map
relief
Geologist
Climate
soil
Cultural map
Political
The population
Economic
transportation
Cultural maps show man-made features. These include population distribution and development, gender and age, social and religious structure, literacy, levels of educational attainment, occupational structure, location of settlements, facilities and services, transport lines and various maps showing the production, distribution and flow of various goods. Huh.
Use of Map
Measurement distance
Straight line by dividers
Curved line is moved along the wheel path by thread or rotameter
Measurement of direction
Area measurement
Measuring squares on illuminated table
The direction is defined as an imaginary straight line on the map that shows a common base direction angular position. The line pointing north is the zero direction or the base direction. A map always shows the north direction. North, South, East and West. These are also called cardinal points.
Area – The total number of ‘perfect squares’ is combined with the ‘partial squares’ .
Area =
The area can also be calculated using a fixed area polar circumference.
Polar Planimeter
The area is also calculated using the Polar Planimeter. In this device, a measurement is made with the motion of a rod, whose position is constrained by fixing one end of the radial arc. The area to be measured is traced along its circumference clockwise with an index mark, starting at a vantage point at which the index of the tracing arm must return exactly. Reading on the dial before and after tracing the perimeter of the field will return a value in instrumental units. These readings are multiplied by the same constant to convert areas in square inches or centimeters by a special device.
Notes of Ch 7 Natural Hazards and Disasters| Class 11th Geography
What is Disaster?
• “Disaster is an undesirable occurrence resulting from forces that are largely outside human control, strikes quickly with little or no warning, which causes or threatens serious disruption of life and property including death and injury to a large number of people, and requires therefore, mobilisation of efforts in excess of that which are normally provided by statutory emergency services”.
• For long time, disasters were considered as consequences of natural forces; and human beings were treated as innocent and helpless victims in front of the mighty forces of nature.
• However natural forces are not only the causes of disasters, but also they can be caused by human activities. There are some other activities of human begings that accelerate or intensityt disasters indirectly.Landslides and floods due to deforestation.The best way out is to emphasise on natural disaster mitigation and management.
Difference between Disaster and Natural Hazard
• Natural hazards are elements of circumstances in the natural environment that have the potential to cause harm to people or property or both.These may be swift or permanent aspects of the respective environmental setting like currents in the oceans.
• As compared to natural hazards, disasters, which are caused by natural forces or activities of human beings, are relatively sudden and cause large scale, widespread death, loss of property and disturbance to social life.
• Natural hazards may be swift or permanent aspects of the respective environmental settings like currents in the ocean , steep slope and unstable structural features in the Himalayas or extreme climatic conditions in deserts or glaciated areas.
• Any event can be classed as disaster when the magnitude of destruction and damage caused by it is very high. Every disaster is unique in terms of the local socio-economic factors that control it, the social response it generates and the way each social group negotiates with it.
Facts about Disaster
• Firstly, the magnitude, intensity, frequency and damages caused by natural disasters have Increased over the years.
• Secondly, there is a growing concern among people the world over to deal with the menace created by these so that the loss of human life and property can be minimised.
• Finally, significant changes have taken place in the pattern of natural disasters over the years.
Modern changes in perception of natural disasters and hazards
• There has also been a change in the perception of natural disasters and hazards.
• Previously hazards and disasters were seen as two closely associated and interrelated phenomena i.e. areas prone to natural hazards, were more vulnerable to disasters. Hence people avoided intensification of their activities in such areas and that is how disasters were less damaging.
• Technological power has given large capacity to human intervention in nature.
• Consequently, now, human beings tend to intensify their activities into disaster prone areas increasing their vulnerability to disasters.
Yokohama Strategy and Plan of Action for a Safer World
• All the member states of the United Nations and other states met at the World Conference on Natural Disaster Reduction in the city of Yokohama from May 23rd-27th 1994.
• The resolution of the World Conference on Natural Disasters Reduction is as mentioned below:
(i) It will note that each country has the sovereign responsibility to protect its citizens from natural disasters;
(ii) It will give priority attention to the developing countries, particularly the least developed, land-locked countries and small-island developing states;
(iii) It will develop and strengthen national capacities and capabilities and, where appropriate, national legislation for natural and other disaster prevention, mitigation and preparedness, including the mobilisation of non-governmental organisations and participation of local communities;
(iv) It will promote and strengthen sub-regional, regional and international cooperation in activities to prevent, reduce and mitigate natural and other disasters, with particular emphasis on: (a) human and institutional capacity-building and strengthening; (b) technology sharing: the collection, the dissemination and utilisation of information; and (c) mobilisation of resources.
• It also declared the decade 1990-2000 as the International Decade for Natural Disaster.
Natural Disasters And Hazards In India Earthquakes
• Earthquakes are by far the most unpredictable and highly destructive of all the natural disasters.
• Earthquakes that are of tectonic origin have proved to be the most devastating and their area of influence is also quite large.
• These earthquakes result from a series of earth movements brought about by a sudden release of energy during the tectonic activities in the earth‘s crust.
• As compared to these, the eart hquakes ass oci at ed with volcanic eruption, rock fall, landslides, subsidence, particularly in the mining areas, impounding of dams and reservoirs, etc. have limited area of influence and the scale of damage.
• The Indian plate is moving at a speed of one centimetre per year towards the north and northeastern direction and this movement of plates is being constantly obstructed by the Eurasian plate from the north.
• As a result of this, both the plates are said to be locked with each other resulting in accumulation of energy at different points of time.
• Excessive accumulation of energy results in building up of stress, which ultimately leads to the breaking up of the lock and the sudden release of energy causes earthquakes along the Himalayan arch.
• Some of the most vulnerable states are Jammu and Kashmir, Himachal Pradesh, Uttarakhand, Sikkim, and the Darjiling and subdivision of West Bengal and all the seven states of the northeast.
• Recently, some earth scientists have come up with a theory of emergence of a fault line and energy build-up along the fault line represented by the river Bhima (Krishna) near Latur and Osmanabad (Maharashtra) and the possible breaking down of the Indian plate.
• National Geophysical Laboratory, Geological Survey of India, Department of Meteorology, Government of India, along with the recently formed National Institute of Disaster Management, following five earthquake zones: → Very high damage risk zone → High damage risk zone → Moderate damage risk zone → Low damage risk zone → Very low damage risk zone.
• North-east states, areas to the north of Darbhanga and Araria along the Indo-Nepal border in Bihar, Uttarakhand, Western Himachal Pradesh (around Dharamshala) are in Very high damage risk zone.
• The remaining parts of Jammu and Kashmir, Himachal Pradesh, Northern parts of Punjab, Eastern parts of Haryana, Delhi, Western Uttar Pradesh, and Northern Bihar fall under the High Damage Risk Zone.
• Remaining parts of the country fall under moderate to very Low Damage Risk Zone. Most of the areas that can be considered safe are from the stable landmass covered under the Deccan plateau.
Socio-Environmental Consequences of Earthquakes
• It becomes a calamity when it strikes the areas of high density of population.
• It not only damages and destroys the settlements, infrastructure, transport and communication network, industries and other developmental activities but also robs the population of their material and socio-cultural gains that they have preserved over generations.
• It renders them homeless, which puts an extra-pressure and stress, particularly on the weak economy of the developing countries.
Effects of Earthquakes
On Ground
On Manmade Structure
On Water
Fissures
Cracking
Waves
Settlements
Slidings
Hydro-Dynamic
Landslides
Overturing
Pressure
Liquefaction
Buckling
Tsunami
Earth Pressure
Collapse
Possible Chain-effects
Possible Chain-effects
Possible Chain-effects
Apart from these , earthquakes also have some serious and far-reaching environment consequences.Earthquakes are also responsible for landslides and often these cause obstructions in the formation of reservoirs.
Earthquake Hazard Mitigation
Methods to decrease the effects of Earthquake
• Establishing earthquake monitoring centres (seismological centres) for regular monitoring and fast dissemination of information among the people in the vulnerable areas. Use of Geographical Positioning System (GPS) can be of great help in monitoring the movement of tectonic plates.
• Preparing a vulnerability map of the country and dissemination of vulnerability risk information among the people and educating them about the ways and means minimising the adverse impacts of disasters.
• Modifying the house types and building designs in the vulnerable areas and discouraging construction of high-rise buildings, large industrial establishments and big urban centres in such areas.
• Finally, making it mandatory to adopt earthquake-resistant designs and use light materials in major construction activities in the vulnerable areas.
Tsunami
• A tsunami is a series of waves caused by an earthquake, underwater volcanic eruption, landslide or other abrupt disturbance.
• The most common cause of atsunami is an earthquake, which is a sudden shifting of the earth’s crust, which releases energy.
• A tsunami can travel as fast as a jet plane in the deep ocean waters.
How is Tsunami formed?
• A tsunami is a series of waves generated in an ocean or other body of water by a disturbance such as an earthquake, landslide, volcanic eruption, or meteorite impact.
• Undersea earthquakes, which typically occur at boundaries between Earth’s tectonic plates, cause the water above to be moved up or down.
Regions affected by Tsunami
• Tsunamis are frequently observed along the Pacific ring of fire, particularly along the coast of Alaska, Japan, Philippines, and other islands of Southeast Asia, Indonesia, Malaysia, Myanmar, Sri Lanka, and India etc.
Effects of Tsunami
• After reaching the coast, the tsunami waves release enormous energy stored in them and water flows turbulently onto the land destroying port cities and towns, structures, buildings and other settlements.
• The effect of tsunami is more along the coast because the density of population is high.
Mitigation
• It is beyond the capacity of individual state or government to mitigate the damage. Hence, combined efforts at the international levels are the possible ways of dealing with these disasters as has been in the case of the tsunami that occurred on 26th December 2004 in which more than 300,000 people lost their lives.
• India has volunteered to join the International Tsunami Warning System after the December 2004 tsunami disaster.
Tropical Cyclone
• Tropical cyclones are intense low- pressure are as confined to the area lying between 30° N
and 30° S latitudes, in the atmosphere around which high velocity winds blow.
• Horizontally, it extends up to 500- 1,000 km and vertically from surface to 12-14 km.
• A tropical cyclone or hurricane is like a heat engine that is energised by the release of latent heat on account of the condensation of moisture that the wind gathers after moving over the oceans and seas.
Initial conditions for the emergence of a tropical cyclone
• Large and continuous supply of warm and moist air that can release enormous latent heat.
• Strong Coriolis force that can prevent filling of low pressure at the centre (absence of Coriolis force near the equator prohibits the formation of tropical cyclone between 0°-5°latitude).
• Unstable condition through the troposphere that creates local disturbances around which a cyclone develops.
• Finally, absence of strong vertical wind wedge, which disturbs the vertical transport of latent heat.
Structure of Tropical Cyclone
• Tropical cyclones are characterised by large pressure gradients. The centre of the cyclone is mostly a warm and low-pressure, cloudless core known as eye of the storm.
• Generally, the isobars are closely placed to each other showing high-pressure gradients. Normally, it varies between 14- 17mb/100 km, but sometimes it can be as high as 60mb/100km. Expansion of the wind belt is about 10-150 km from the centre.
Spatio-temporal Distribution of Tropical Cyclone in India
• The tropical cyclones in India originate in Arabian sea in the west and Bay of Bengal in the east.
• Though most of the cyclones originate between 10°-15° north latitudes during the monsoon season, yet in case of the Bay of Bengal, cyclones mostly develop during the months of October and November. Here, they originate between 16°-2° N latitudes and to the west of 92° E. By July the place of origin of these storms shifts to around 18° N latitude and west of 90°E near the Sunderban Delta.
Consequences of Tropical Cyclones
• It was mentioned that the energy to the tropical cyclone comes from the latent heat released by the warm moist air. Hence, with the increase in distance from the sea, the force of the cyclone decreases.
• In India, the force of the cyclone decreases with increase in distance from the Bay of Bengal and the Arabian Sea. So, the coastal areas are often struck by severe cyclonic storms with an average velocity of 180 km/h.
• Often, tropical cyclone results in abnormal rise in the sea level known as Storm Surge. A surge is generated due to interaction of air, sea and land.
• The cyclone provides the driving force in the form of very high horizontal pressure-gradient and very strong surface winds.
• The sea water flows across the coast along with strong winds and heavy downpour. This results in inundation of human settlements, agricultural fields, damaging crops and destruction of structures created by human beings.
Floods
• Floods occur commonly when water in the form of surface run-off exceeds the carrying capacity if the river channels and streams and flows into the neighbouring low-lying flood plains.
Causes of Floods
• A flood occurs when a river bursts its banks and the water spills onto the floodplain.
• Flooding tends to be caused by heavy rain: the faster the rainwater reaches the river channel, the more likely it is to flood.
Regions affected by Floods
• Floods in the South, Southeast and East Asian countries, particularly in China, India and Bangladesh are frequent and equally disastrous.
Areas of India frequently affected by floods
Rashtriya Barh Ayog (National Flood Commission) identified 40 million hectares of land as flood- prone in India.
• Assam, West Bengal and Bihar are among the high flood- prone states of India.
• Most of the rivers in the northern states like Punjab and Uttar Pradesh are also ulnerable to occasional floods.
• States like Rajasthan, Gujarat, Haryana and Punjab are also getting inundated in recent decades due to flash floods.
• Tamil Nadu experiences flooding during November- January due to the retreating monsoon.
Consequence and Control of Floods
Frequent inundation of agricultural land and human settlement, particularly in Assam, West Bengal, Bihar and Eastern Uttar Pradesh (flooding rivers), coastal areas of Orissa, Andhra Pradesh, Tamil Nadu and Gujarat (cyclone) and Punjab, Rajasthan, Northern Gujarat and Haryana (flash floods) have the following consequences:
• Floods seriously affect the national economy and society.
• Floods destroy valuable crops every year.
• Floods also damage physical infrastructure such as roads, rails, bridges and human settlements.
• Millions of people are rendered homeless and are also washed down along with their cattle in the floods.
• Spread of diseases like cholera, gastro-enteritis, hepatitis and other water-borne diseases spread in the flood-affected areas.
• The only positive consequence of Flooding is deposition of fertile silt over agricultural fields which is good for the crops, every year. Majuli (Assam), the largest riverine island in the world, is the best example of good paddy crops after the annual floods in Brahmaputra.
Methods to Control the Floods
• In many countries, rivers prone to floods are often carefully managed. Defences such as levees, bunds, reservoirs, and weirs are used to prevent rivers from bursting their banks.
• When these defences fail, emergency measures such as sandbags or portable inflatable tubes are used.
• Coastal flooding has been addressed in Europe and the Americas with coastal defences, such as sea walls, beach nourishment, and barrier islands.
• A dike is another method of flood protection. A dike lowers the risk of having floods compared to other methods. It can help prevent damage; however it is better to combine dikes with other flood control methods to reduce the risk of a collapsed dike.
• A weir, also known as a lowhead dam, is most often used to create millponds, but on the Humber River in Toronto, a weir was built near Raymore Drive to prevent a recurrence of the flooding caused by Hurricane Hazel in 1954, which destroyed nearly two fifths of the street.
Droughts
• The term ‘drought’ is applied to an extended period when there is a shortage of water availability due to inadequate precipitation, excessive rate of evaporation and over-utilisation of water from the reservoirs and other storages, including the ground water.
Drought is a complex phenomenon as it involves elements of meteorology like
(i) Precipitation (ii) Evaporation, (iii) Evapotranspiration, (iv) Ground water, (v) Soil moisture, (vi) Storage of water, (vii) Surface run-off, (viii) Agricultural practices, particularly the types of crops grown, (ix) Socio-economic practices (x) Ecological conditions
Types of Droughts
• Meteorological Drought: It is a situation when there is a prolonged period of inadequate rainfall marked with mal-distribution of the same over time and space.
• Agricultural Drought: It is also known as soil moisture drought, characterised by low soil moisture that is necessary to support the crops, thereby resulting in crop failures. Moreover, if an area has more than 30 per cent of its gross cropped area under irrigation, the area is excluded from the drought-prone category.
• Hydrological Drought: It results when the availability of water in different storages and reservoirs like aquifers, lakes, reservoirs, etc. falls below what the precipitation can replenish.
• Ecological Drought: When the productivity of a natural ecosystem fails due to shortage of water and as a consequence of ecological distress, damages are induced in the ecosystem.
Drought Prone Areas in India
• Droughts and floods are the two accompanying features of Indian climate.
• According to some estimates, nearly 19 per cent of the total geographical area of the country and 12 percent of its total population suffer due to drought every year.
• About 30 percent of the country’s total area is identified as drought prone affecting around 50 million people.
• It is a common experience that while some parts of the country reel under floods, there are regions that face severe drought during the same period.
• Also, it is also a common sight to witness that one region suffers due to floods in one season and experiences drought in the other. This is mainly because of the large-scale variations and unpredictability in the behaviour of the monsoon in India.
On the basis of severity of droughts, India can be divided into the following regions:
• Extreme Drought Affected Area: Most parts of Rajasthan, particularly areas to the west of the Aravali hills, i.e.. Marusthali and Kachchh regions of Gujarat fall in this category. Included here are also the districts like Jaisalmer and Barmer from the Indian desert that receive less that 90 mm average annual rainfall.
• Severe Drought Prone Area: Parts of eastern Rajasthan, most parts of Madhya Pradesh, eastern parts of Maharashtra, interior parts of Andhra Pradesh and Karnataka Plateau, northern parts of interior Tamil Nadu and southern parts of Jharkhand and interior Orissa are included in this category.
• Moderate Drought Affected Area: Northern parts of Rajasthan, Haryana, southern districts of Uttar Pradesh, the remaining parts of Gujarat, Maharashtra except Konkan, Jharkhand and Coimbatore plateau of Tamil Nadu and interior Karnataka are included in this category.
• The remaining parts of India can be considered either free or less prone to the drought.
Consequences of Drought
Droughts have both immediate as well as long term disastrous consequences on the social and physical environments.
• Crop failure leading to scarcity of food grains (akal) and fodder (trinkal), inadequate rainfall, resulting in shortage of water (jalkal), and often shortage in all the three, i.e. food grains, fodder and water (trikal) is most devastating.
• Large-scale death of cattle and other animals.
• Migration of humans and livestock are the most common sight to be seen in the drought affected areas.
• Scarcity of water compels people to consume contaminated water resulting in spread of many waterborne diseases like gastro-enteritis, cholera, hepatitis, etc.
Mitigation
• Provision for the distribution of safe drinking water.
• Medicines for the victims.
• Availability of fodder and water for the cattle.
• Shifting of the people and their livestock to safer places.
• Identification of ground water potential in the form of aquifers.
• Transfer of river water from the surplus to the deficit areas.
• Planning for inter-linking of rivers.
• Construction of reservoirs and dams.
• Remote sensing and satellite imageries can be useful in identifying the possible river-basins that can be inter-linked and in identifying the ground water potential.
• Dissemination of knowledge about drought-resistant crops and proper training to practice the same can be some of the long-term measures that will be helpful in drought-mitigation.
• Rainwater harvesting can also be an effective method in minimising the effects of drought.
Landslides
• Landslides are largely controlled by highly localised factors. Hence, gathering information and monitoring the possibilities of landslide is not only difficult but also immensely cost-intensive.
• It is always difficult to define in a precise statement and generalise the occurrence and behaviour of a landslide.
Controlling Factors
• Geology
• Geomorphic agents
• Slope
• Land-use
• Vegetation cover
• Human activities
Landslide Vulnerability Zones of India
India has been divided into a number of zones:
• Very High Vulnerability Zone: Highly unstable, relatively young mountainous areas in the Himalayas and Andaman and Nicobar, high rainfall regions with steep slopes in the Western Ghats and Nilgiris, the north-eastern regions, along with areas that experience frequent ground-shaking due to earthquakes, etc. and areas of intense human activities, particularly those related to construction of roads, dams, etc. are included in this zone.
• High Vulnerability Zone: Areas that have almost similar conditions to those included in the very high vulnerability zone are also included in this category. The only difference between these two is the combination, intensity and frequency of the controlling factors. All the Himalayan states and the states from the north-eastern regions except the plains of Assam are included in the high vulnerability zones.
• Moderate to Low Vulnerability Zone: Areas that receive less precipitation such as Trans Himalayan areas of Ladakh and Spiti (Himachal Pradesh), undulated yet stable relief and low precipitation areas in the Aravali, rain shadow areas in the Western and Eastern Ghats and Deccan plateau also experience occasional landslides. Landslides due to mining and subsidence are most common in states like Jharkhand, Orissa, Chhattisgarh, Madhya Pradesh, Maharashtra, Andhra Pradesh, Karnataka, Tamil Nadu, Goa and Kerala.
• Other Areas: The remaining parts of India, particularly states like Rajasthan, Haryana, Uttar Pradesh, Bihar, West Bengal (except district Darjiling), Assam (except district Karbi Anglong) and Coastal regions of the southern States are safe as far as landslides are concerned.
Consequences of Landslides
• Roadblock,
• Destruction of railway lines,
• Channel-blocking due to rock-falls have far-reaching consequences,
• Diversion of river courses due to landslides can also lead to flood,
• Loss of life and property,
• Difficult spatial interaction which adversely affects the developmental activities in these areas.
Mitigation
• Restriction on the construction and other developmental activities such as roads and dams,
• Limiting agriculture to valleys and areas with moderate slopes,
• Control on the development of large settlements in the high vulnerability zones,
• Promoting large-scale afforestation programmes
• Construction of bunds to reduce the flow of water.
• Terrace farming should be encouraged in the northeastern hill states where Jhumming (Slash and Burn/Shifting Cultivation) is still prevalent.
Disaster Management
• Disaster Management refers to how we can protect or preserve many lives and property.
• India has been traditionally vulnerable to the natural disasters on the account of its unique geo climatic conditions.
• Floods, droughts, cyclones, earthquakes and landslides would have been a recurrent phenomena.The steps that can help in minimising the damages of cyclones are: → Construction of cyclone shelters, embankments, dykes, reservoirs, Afforestation to reduce the speed of the winds, → implementation of The Disaster Management Bill, 2005.
Conclusion
Mitigation and Preparedness
There are three stages involved in disaster mitigation and management:
(i) Pre-disaster management involves • Generating data and information about the disasters, • Preparing vulnerability zoning maps, • Spreading awareness among the people about the disasters, • Disaster planning, • Preparedness and preventive measures are other steps that need to be taken in the vulnerable areas.
(ii) During disasters, Rescue and relief operations such as evacuation, construction of shelters, relief camps, supplying of water, food, clothing and medical aids etc. should be done on an emergency basis.
(iii) Post-disaster operations should involve: • rehabilitation • recovery of victims. • concentrate on capacity building in order to cope up with future disasters.
These measures have special significance to a country like India. Introduction of the Disaster Management Bill, 2005 and establishment of National Institute of Disaster Management are some examples of positive steps taken by Government of India.
Soil is the mixture of rock debris and organic materials which develop on the earth’s surface.
The major factors affecting the formation of soil are relief, parent material, climate, vegetation and other life-forms and time. Besides these, human activities also influence it to a large extent.
Components of the soil are mineral particles, humus, water and air. The actual amount of each of these depends upon the type of soil.
Soil is bifurcated into three layers called horizons. ‘Horizon A’ is the topmost zone, where organic materials have got incorporated with the mineral matter, nutrients and water, which are necessary for the growth of plants. ‘Horizon B’ is a transition zone between the ‘horizon A’ and ‘horizon C’, and contains matter derived from below as well as from above. It has some organic matter in it, although the mineral matter is noticeably weathered. ‘Horizon C’ is composed of the loose parent material. This layer is the first stage in the soil formation process and eventually forms the above two layers.
In ancient times, soils used to be classified into twro main groups – Urvara and Usara, which were fertile and sterile, respectively.
In the 16th century A.D., soils were classified on the basis of their inherent characteristics and external features such as texture, colour, slope of land and moisture content in the soil. Based on texture, main soil types were identified as sandy, clayey, silty and loamy, etc. On the basis of colour, they wrere red, yellow, black, etc.
On the basis of genesis, colour, composition and location, the soils of India have been classified into:
Alluvial soils
Black soils
Red and Yellow soils
Laterite soils
Arid soils
Saline soils
Peaty soils
Forest soils.
Alluvial Soils Alluvial soils are widespread in the northern plains and the river valleys. These soils cover about 40 per cent of the total area of the country. They are depositional soils, transported and deposited by rivers and streams.
The alluvial soils vary in nature from sandy loam to clay. They are generally rich in potash but poor in phosphorous. In the Upper and Middle Ganga plain, two different types of alluvial soils have developed, viz. Khadar and Bhangar.
Khadar is the new alluvium and is deposited by floods annually, which enriches the soil by depositing fine silts. Bhangar represents a system of older alluvium, deposited away from the flood plains.
Black soil covers most of the Deccan Plateau which includes parts of Maharashtra, Madhya Pradesh, Gujarat, .Andhra Pradesh and some parts of Tamil Nadu. In the upper reaches of the Godavari and the Krishna, and the north western part of the Deccan Plateau, the black soil is very deep.
Red soil develops on crystalline igneous rocks in areas of low rainfall in the eastern and southern part of the Deccan Plateau. Along the piedmont zone of the Western Ghat, long stretch of area is occupied by red loamy soil.
Laterite has been derived from the Latin word ‘Later’ which means brick. The laterite soils develop in areas with high temperature and high rainfall. These are the result of intense leaching due to tropical rains. With rain, lime and silica are leached away, and soils rich in iron oxide and aluminium compound are left behind.
Arid soils range from red to brown in colour. They are generally sandy in structure and saline in nature. In some areas, the salt content is so high that common salt is obtained by evaporating the saline water. Due to the dry climate, high temperature and accelerated evaporation, they lack moisture and humus.
Saline soils are also known as Usara soils. Saline soils contain a larger proportion of sodium, potassium and magnesium, and thus, they are infertile, and do not support any vegetative growth. They have more salts, largely because of dry climate and poor drainage. They occur in arid and semi-arid regions, and in waterlogged and swampy areas.
Peaty soils are found in the areas of heavy rainfall and high humidity, where there is a good growth of vegetation. Thus, large quantity of dead organic matter accumulates in these areas, and this gives a rich humus and organic content to the soil. Organic matter in these soils may go even up to 40-50 per cent.
Forest soils are formed in the forest areas where sufficient rainfall is available. The soils vary in structure and texture depending on the mountain environment where they are formed. They are loamy and silty on valley sides and coarse-grained in the upper slopes.
Soil degradation can be defined as the decline in soil fertility, when the nutritional status declines and depth of the soil goes down due to erosion and misuse. Soil degradation is the main factor leading to the depleting soil resource base in India. The degree of soil degradation varies from place to place according to the topography, wind velocity and amount of the rainfall.
The destruction of the soil cover is described as soil erosion. Forest and other natural vegetation are removed for human settlement, for cultivation, for grazing animals and for various other needs. Wind and water are powerful agents of soil erosion because of their ability to remove soil and transport it.
Soil erosion is a serious problem for Indian agriculture and its negative eff ects are seen in other spheres also. Eroded materials are carried down to rivers and they lower down their carrying capacity, and cause frequent floods and damage to agricultural lands.
Deforestation is one of the major causes of soil erosion. Plants keep soils bound in locks of roots, and thus, prevent erosion. They also add humus to the soil by shedding leaves and twigs. The salt lodged in the lower profiles of the soil comes up to the surface and destroys its fertility. Chemical fertilizers in the absence of organic manures are also harmful to the soil.
If soil erosion and exhaustion are caused by humans; by corollary, they can also be prevented by humans. Contour bunding, Contour terracing, regulated forestry, controlled grazing, cover cropping, mixed farming and crop rotation are some of the remedial measures which are often adopted to reduce soil erosion.
Experiments have been made to stabilize sand dunes in western Rajasthan by the Central Arid Zone Research Institute (CAZRI). The Central Soil Conservation Board, set up by the Government of India, has prepared a number of plans for soil conservation in different parts of the country.
Important Soils Found In India:
Class 11 Geography Notes Chapter 6 Important Terms:
Soil: Soil is the mixture of rock debris and organic materials which develop on the earth’s surface.
Bad land topography: A region with a large number of deep gullies or ravines is called a bad land topography.
Horizons: When we dig a pit on land and look at the soil, we find that it consists of three layers. These are called horizons.
Horizon A: It is the topmost zone, where organic materials have got incorporated with the • mineral matter, nutrients and water, which are necessary for the growth of plants.
Horizon B: It is a transition zone between the ‘horizon A’ and ‘horizon C’, and contains matter derived from below as well as from above. It has some organic matter in it, although the mineral matter is noticeably weathered.
Horizon C: It is composed of the loose parent material. This layer is the first stage in the soil formation process and eventually forms the above two layers.
Soil profile: The arrangement of layers in three horizons, A, B and C is known as the soil profile.
Parent rock: Underneath the three horizons there is the rock which is known as the parent rock or the bedrock.
Estuary: The tidal mouth of a river where fresh and saline water get mixed.
Gully erosion: It is the erosion of the soil and rock by the concentration of runoff into gullies.
Humus: The dead organic content of the soil.
Khadar: Khadar is the new alluvium and is deposited by floods annually, which enriches the soil by depositing fine silts.
Bhangar: Bhangar represents a system of older alluvium, deposited away from the flood plains.
Alluvial soil: They are depositional soils, transported and deposited by rivers and streams.
Laterite soil: Laterite has been derived from the Latin word ‘Later’ which means brick. The laterite soils develop in areas with high temperature and high rainfall.
Black soil: These soils are made from volcanoes. These soils are also known as the ‘RegurSoil’ or the ‘Black Cotton Soil’.
Forest soils: Forest soils are formed in the forest areas where sufficient rainfall is available.
Peaty soils: They are found in the areas of heavy rainfall and high humidity, where there is a good growth of vegetation.
Soil erosion: The destruction of the soil cover is described as soil erosion.
Soil degradation: Soil degradation can be defined as the decline in soil fertility, when the nutritional status declines and depth of the soil goes down due to erosion and misuse. Soil degradation is the main factor leading to the depleting soil resource base in India.
Soil Conservation: Soil conservation is a methodology to maintain soil fertility, prevent soil erosion and exhaustion, and improve the degraded condition of the soil.
Notes of Ch 5 Natural Vegetation| Class 11th Geography
Introduction
• Natural vegetation refers to a plant community that has been left undisturbed over a long time, so as to allow its individual species to adjust themselves to climate and soil conditions as fully as possible.
• Himalayan heights are marked with the different types of vegetation according to altitude.
• The Western and Eastern Ghats and the Andaman Nicobar Islands have tropical rain forests while the deltaic regions have tidal forests (mangroves). The desert and semi-desert areas of Rajasthan are known for cactii, a wide variety of bushes and thorny vegetation.
• Depending upon the variations in the climate and the soil, the vegetation of India changes from one region to another.
• On the basis of certain common features such as predominant vegetation type and climatic regions, Indian forests can be divided into various groups.
Types of Forests
(i) Tropical Evergreen and Semi Evergreen forests (ii) Tropical Deciduous forests (iii) Tropical Thorn forests (iv) Montane forests (v) Littoral and Swamp forests
The Tropical Evergreen and Semi Evergreen forests
• These forests are found in the western slope of the Western Ghats, Eastern slopes of eastern Ghats, hills of the northeastern states and the Andaman and Nicobar Islands.
• They are found in warm and humid areas with an annual precipitation of over 200 cm and mean annual temperature above 22° C.
• Tropical evergreen forests are well stratified, with layers closer to the ground and are covered with shrubs and creepers, with short structured trees followed by tall variety of trees.
• Trees reach great heights up to 60 m or above.
• There is no definite time for trees to shed their leaves, flowering and fruition. As such these forests appear green all the year round.
• Species found in these forests include rosewood, mahogany, aini, ebony, etc.
Semi Evergreen Forest
• The semi evergreen forests are found in the less rainy parts of these regions.
• Such forests have a mixture of evergreen and moist deciduous trees.
• The under growing climbers provide an evergreen character to these forests.
• Main species are white cedar, hollock and kail.
• The oak forests in Garhwal and Kumaon were replaced by pine (chirs) which was needed to lay railway lines.
• Forests were also cleared for introducing plantations of tea, rubber and coffee.
Tropical Deciduous Forests
• These are the most widespread forests in India.
• They are also called the monsoon forests.
• They spread over regions which receive rainfall between 70-200 cm.
• On the basis of the availability of water, these forests are further divided into moist and dry deciduous.
Moist deciduous forests
• They are mostly found in the regions which record rainfall between 100-200 cm.
• These forests are found in the northeastern states along the foothills of the Himalayas, eastern slopes of the Western Ghats and Odisha.
• Teak, sal, shisham, mahua, amla, semul, kusum, and sandalwood etc. are the main species of these forests.
Dry deciduous forests
• Covers vast areas of the country.
• Rainfall ranges between 70 -100 cm.
• On the wetter margins, it has a transition to the moist deciduous, while on the drier margins to thorn forests.
• These forests are found in rainier areas of the Peninsula and the plains of Uttar Pradesh and Bihar.
• Parklands are found In the higher rainfall regions of the Peninsular plateau and the northern Indian plain.
• As the dry season begins, the trees shed their leaves completely and the forest appears like a vast grassland with naked trees all around.
• Tendu, palas, amaltas, bel, khair, axlewood, etc. are the common trees of these forests.
• In the western and southern part of Rajasthan, vegetation cover is very scanty due to low rainfall and overgrazing.
Tropical Thorn Forests
• Tropical thorn forests occur in the areas which receive rainfall less than 50 cm.
• These consist of a variety of grasses and shrubs.
• It includes semi-arid areas of south-west Punjab, Haryana, Rajasthan, Gujarat, Madhya Pradesh and Uttar Pradesh.
• In these forests, plants remain leafless for the most part of the year and give an expression of scrub vegetation.
• Important species found are babool, ber, and wild date palm, khair, neem, khejri, palas, etc.
• Tussocky grass grows upto a height of 2 m as the under growth.
Montane Forests
• In mountainous areas, the decrease in temperature with increasing altitude leads to a corresponding change in natural vegetation.
• Mountain forests can be classified into two types, the northern mountain forests and the southern mountain forests.
• The Himalayan ranges show a succession of vegetation from the tropical to the tundra, which changes in with the altitude.
• Deciduous forests are found in the foothills of the Himalayas.
• It is succeeded by the wet temperate type of forests between an altitude of 1,000-2,000 m.
Littoral And Swamp Forests
• India’s wetlands have been grouped into eight categories:
(i) The Reservoirs of the Deccan plateau in the south together with the lagoons and other wetlands of southern west coast.
(ii) The vast saline expenses of Rajasthan Gujarat and the Gulf of Kachchhh.
(iii) Freshwater lakes and reservoirs from Gujarat eastward through Rajasthan (Keoladev National park) and Madya Pradesh.
(iv) The delta wetlands and lagoons of India’s east coast (Chilika Lake).
(v) The freshwater marshes of the Gangetic Plain.
(vi) The floodplains of the Brahmaputra, the marshes and swamps in the hills of northeast India and the Himalayan foothills.
(vii) The lakes and rivers of the montane region of Kashmir and Ladakh.
(viii) The mangrove forest and other wetlands of the island arcs of Andaman and Nikobar Islands.
• In India, the mangrove forests spread over 6,740 sq. km which is 7 percent of the world’s mangrove forests. They are developed in Andaman and Nicobar Islands, Sunderbans of West Bengal, the Mahanadi, the Godavari and the Krishna deltas.
Climate refers to the average of the weather condition over a longer period of time.
Weather changes quickly, may be within a day or week
Climate changes imperceptibly and may be noted after 50 years or even more
Unity And Diversity In The Monsoon Climate Unity of The Climate
• The monsoon regime emphasizes the unity of India with the rest of southeast Asian region.
• This view of broad unity of the monsoon type of climate should not, however, lead one to ignore its regional variations which differentiate the weather and climate of different regions of India.
• The climate of Kerala and Tamil Nadu in the south are so different from that of Uttar Pradesh and Bihar in the north, and yet all of these have a monsoon type of climate.
Diversity of Climate
• The climate of India has many regional variations expressed in the pattern of: → Winds, → Temperature → Rainfall, → Rhythm of seasons → Degree of wetness or dryness.
Temperature Variation
• While in the summer the mercury occasionally touches 55°C in the western Rajasthan, it drops down to as low as minus 45°C in winter around Leh.
• Churu in Rajasthan may record a temperature of 50°C or more on a June day while the mercury hardly touches 19°C in Tawang (Arunachal Pradesh) on the same day.
• On a December night, temperature in Drass (Jammu and Kashmir) may drop down to minus 45°C while Thiruvananthapuram or Chennai on the same night records 20°C or 22°C.
• In Kerala and in the Andaman Islands, the difference between day and night temperatures may be hardly seven or eight degree Celsius. But in the Thar desert, if the day temperature is around 50°C, at night, it may drop down considerably up to 15°-20°C.
The Regional Variations In Precipitation
• While snowfall occurs in the Himalayas, it only rains over the rest of the country.
• While Cherrapunji and Mawsynramin the Khasi Hills of Meghalaya receive rainfall over 1,080 cm in a year, Jaisalmer in Rajasthan rarely gets more than 9 cm of rainfall during the same period.
• Tura situated in the Garo Hills of Meghalaya may receive an amount of rainfall in a single day which is equal to 10 years of rainfall at Jaisalmer.
• While the annual precipitation is less than 10 cm in the northwest Himalayas and the western deserts, it exceeds 400 cm in Meghalaya.
• The Ganga delta and the coastal plains of Odisha are hit by strong rain-bearing storms almost every third or fifth day in July and August while the Coromandal coast, a thousand km to the south, goes generally dry during these months.
• Most parts of the country get rainfall during June-September, but on the coastal areas of Tamil Nadu, it rains in the beginning of the winter season.
Factors Determining The Climate Of India
• It can be broadly divided into two groups factors: → Factors related to location and relief → Factors related to air pressure and winds
Factors related to Location and Relief
• Latitude: Northern part of the India lies in sub-tropical and temperate zone and the part lying south of the Tropic of Cancer falls in the tropical zone. The tropical zone being nearer to the equator, experiences high temperatures throughout the year with small daily and annual range. Area north of the Tropic of Cancer being away from the equator experiences extreme climate with high daily and annual range of temperature.
• The Himalayan Mountains: The lofty Himalayas in the north along with its extensions act as an effective climatic divide. The towering mountain chain provides an invincible shield to protect the subcontinent from the cold northern winds. The Himalayas also trap the monsoon winds, forcing them to shed air pressure causes reversal in the direction of monsoon winds.
• Distance from the Sea: With a long coastline, large coastal areas have an equable climate. Areas in the interior of India are far away from the moderating influence of the sea. Such areas have extremes of climate their moisture within the subcontinent.
• Distribution of Land and Water: India is flanked by the Indian Ocean on three sides in the south and girdled by a high and continuous mountain-wall in the north. As compared to the landmass, water heats up or cools down slowly. This differential heating of land and sea creates different air pressure zones in different seasons in and around the Indian subcontinent.
• Difference in Altitude: Temperature decreases with height. Due to thin air, places in the mountains are cooler than places on the plains.
• Relief: The physiography or relief of India also affects the temperature, air pressure, direction and speed of wind and the amount and distribution of rainfall. The windward sides of Western Ghats and Assam receive high rainfall during June-September whereas the southern plateau remains dry due to its leeward situation along the Western Ghats.
Factors Related to Air Pressure and Wind
• Distribution of air pressure and winds on the surface of the earth.
• Upper air circulation caused by factors controlling global weather and the inflow of different air masses and jet streams.
• Inflow of western cyclones generally known as disturbances during the winter season and tropical depressions during the south-west monsoon period into India, creating weather conditions favourable to rainfall.
Mechanism of Weather in the Winter Season Surface Pressure and Winds
• In winter months, the weather conditions over India are generally influenced by the distribution of pressure in Central and Western Asia.
• A high pressure centre in the region lying to the north of the Himalayas develops during winter. This centre of high pressure gives rise to the flow of air at the low level from the north towards the Indian subcontinent, south of the mountain range.
• The surface winds blowing out of the high pressure centre over Central Asia reach India in the form of a dry continental air mass. These continental winds come in contact with trade winds over northwestern India.
Jet Stream and Upper Air Circulation
• Higher up in the lower troposphere, about three km above the surface of the earth, a different pattern of air circulation is observed.
• The variations in the atmospheric pressure closer to the surface of the earth have no role to play in the making of upper air circulation.
• All of Western and Central Asia remains under the influence of westerly winds along the altitude of 9-13 km from west to east.
• These winds blow across the Asian continent at latitudes north of the Himalayas roughly parallel to the Tibetan highlands. These are known as jet streams. branch blows in an eastward direction, south of the Himalayas.
• It has its mean position at 25°N in February at 200-300 mb level. It is believed that this southern branch of the jet stream exercises an important influence on the winter weather in India.
Direction of Winds in India in Winter at the Height of 9-13 km Western Cyclonic Disturbance and Tropical Cyclones
• The western cyclonic disturbances which enter the Indian subcontinent from the west and the northwest during the winter months, originate over the Mediterranean Sea and are brought into India by the westerly jet stream.
• An increase in the prevailing night temperature generally indicates an advance in the arrival of these cyclones disturbances.
• Tropical cyclones originate over the Bay of Bengal and the Indian ocean.
• These tropical cyclones have very high wind velocity and heavy rainfall and hit the Tamil Nadu, Andhra Pradesh and Orissa coast.
• Most of these cyclones are very destructive due to high wind velocity and torrential rain that accompanies.
Mechanism of Weather in the Summer Season Surface Pressure and Winds
• As the summer sets in and the sun shifts northwards, the wind circulation over the subcontinent undergoes a complete reversal at both, the lower as well as the upper levels.
• By the middle of July, the low pressure belt nearer the surface [termed as Inter Tropical Convergence Zone (ITCZ)] shifts northwards, By this time, the westerly jet stream withdraws from the Indian region.
• It is generally believed that there is a cause and effect relationship between the ictz and jet stream.
• The ITCZ being a zone of low pressure, attracts inflow of winds from different directions.
• The maritime tropical airmass (mT) from the southern hemisphere, after crossing the equator, rushes to the low pressure area in the general southwesterly direction. It is this moist air current which is popularly known as the southwest monsoon.
Jet Streams and Upper Air Circulation
• An easterly jet stream flows over the southern part of the Peninsula in June, and has a maximum speed of 90 km per hour.
• In August, it is confined to 15oN latitude, and in September up to 22o N latitudes. The easterlies normally do not extend to the north of 30o N latitude in the upper atmosphere.
Easterly Jet Stream and Tropical Cyclones
• The easterly jet stream steers the tropical depressions into India.
• These depressions play a significant role in the distribution of monsoon rainfall over the Indian subcontinent.
• The tracks of these depressions are the areas of highest rainfall in India.
• The frequency at which these depressions visit India, their direction and intensity, all go a long way in determining the rainfall pattern during the southwest monsoon period.
The Inter Tropical Convergence Zone (ITCZ)
• A low pressure zone located at the equator where trade winds converge, and so, it is a zone where air tends to ascend.
• In July, the ITCZ is located around 20°N-25°N latitudes (over the Gangetic plain), sometimes called the monsoon trough.
• This monsoon trough encourages the development of thermal low over north and northwest India.
• Due to the shift of ITCZ, the trade winds of the southern hemisphere cross the equator between 40° and 60°E longitudes and start blowing from southwest to northeast due to the Coriolis force. It becomes southwest monsoon.
• In winter, the ITCZ moves southward, and so the reversal of winds from northeast to south and southwest, takes place. They are called northeast monsoons.
The Nature Of Indian Monsoon
(i) The onset of the monsoon.
(ii) Rain-bearing systems (e.g. tropical cyclones) and the relationship between their
frequency and distribution of monsoon rainfall.
(iii) Break in the monsoon.
Onset of the Monsoon
• During April and May when the sun shines vertically over the Tropic of Cancer, the large landmass in the north of Indian ocean gets intensely heated. This causes the formation of an intense low pressure in the northwestern part of the subcontinent.
• Since the pressure in the Indian Ocean in the south of the landmass is high as water gets heated slowly, the low pressure cell attracts the southeast trades across the Equator.
• These conditions help in the northward shift in the position of the ITCZ. The southwest monsoon may thus, be seen as a continuation of the southeast trades deflected towards the Indian subcontinent after crossing the Equator. These winds cross the Equator between 40°E and 60°E longitudes.
Entry of Monsoon into India
• The southwest monsoon sets in over the Kerala coast by 1st June and moves swiftly to reach Mumbai and Kolkata between 10th and 13th June. By mid July, southwest monsoon engulfs the entire subcontinent.
Rain-bearing Systems and Rainfall Distribution
• Bay of Bengal Branch • Arabian sea branch
The rainfall distribution is based on two factors:
(i) The offshore meteorological conditions.
(ii) The position of the equatorial jet stream along the eastern coast of Africa.
EI-Nino and the Indian Monsoon
• EI-Nino is a complex weather system that appears once every three to seven years, bringing drought, floods and other weather extremes to different parts of the world.
• The system involves oceanic and atmospheric phenomena with the appearance of warm currents off the coast of Peru in the Eastern Pacific and affects weather in many places including India.
• EI-Nino is merely an extension of the warm equatorial current which gets replaced temporarily by cold Peruvian current or Humbolt current (locate these currents in your atlas). This current increases the temperature of water on the Peruvian coast by 10°C. This results in: (i) the distortion of equatorial atmospheric circulation; (ii) irregularities in the evaporation of sea water; (iii) reduction in the amount of planktons which further reduces the number of fish in the sea.
• The word EI-Nino means ‘Child Christ’ because this current appears around Christmas in December. December is a summer month in Peru (Southern Hemisphere).
• EI-Nino is used in India for forecasting long range monsoon rainfall. In 1990-91, there was a wild EI-Nino event and the onset of southwest monsoon was delayed over most parts of the country ranging from five to twelve days.
Break in the Monsoon
• During the south-west monsoon period after having rains for a few days, if rain fails to occur for one or more weeks, it is known as break in the monsoon.
• These dry spells are quite common during the rainy season. These breaks in the different regions are due to different reasons:
(i) In northern India rains are likely to fail if the rain-bearing storms are not very frequent along the monsoon trough or the ITCZ over this region. (ii) Over the west coast the dry spells are associated with days when winds blow parallel to the coast.
The Rhythm Of Seasons
The climatic conditions of India can best be described in terms of an annual cycle of seasons. Four seasons are: (i) The cold weather season (ii) The hot weather season
(iii) The southwest monsoon season
(iv) The retreating monsoon season
The Cold Weather Season
• Found from November to February
• December and January are the coldest months in the northern plain.
• The mean daily temperature remains below 21°C, over most parts of northern India.
• The night temperature may be quite low, sometimes going below freezing point in Punjab and Rajasthan.
There are three main reasons for the excessive cold in north India during this season: (i) States like Punjab, Haryana and Rajasthan being far away from the moderating influence of sea experience continental climate.
(ii) The snowfall in the nearby Himalayan ranges creates cold wave situation; and
(iii) Around February, the cold winds coming from the Caspian Sea and Turkmenistan bring cold wave along with frost and fog over the northwestern parts of India.
Pressure and Winds:
• By the end of December (22nd December), the sun shines vertically over the Tropic of Capricorn in the southern hemisphere.
• The weather in this season is characterized by feeble high pressure conditions over the northern plain. In south India, the air pressure is slightly lower respectively.
• As a result, winds start blowing from northwestern high pressure zone to the low air pressure zone over the Indian Ocean in the south. Due to low pressure gradient, the light winds with a low velocity of about 3-5 km per hour begin to blow outwards.
• By and large, the topography of the region influences the wind direction. They are westerly or northwesterly down the Ganga Valley. They become northerly in the Ganga-Brahmaputra delta. Free from the influence of topography, they are clearly northeasterly over the Bay of Bengal.
• During the winters, the weather in India is pleasant.
• The pleasant weather conditions, however, at intervals, get disturbed by shallow cyclonic depressions originating over the east Mediterranean Sea and travelling eastwards across West Asia, Iran, Afghanistan and Pakistan before they reach the northwestern parts of India.
Rainfall:
• Winter monsoons do not cause rainfall as they move from land to the sea.
• It is because firstly, they have little humidity;
• Secondly, due to anti cyclonic circulation on land, the possibility of rainfall from them reduces. So, most parts of India do not have rainfall in the winter season.
However, there are some exceptions to it:
• In northwestern India, some weak temperate cyclones from the Mediterranean sea cause rainfall in Punjab, Haryana, Delhi and western Uttar Pradesh. Although the amount is meagre, it is highly beneficial for Rabi crops. The precipitation is in the form of snowfall in the lower Himalayas. It is this snow that sustains the flow of water in the Himalayan rivers during the summer months. The precipitation goes on decreasing from west to east in the plains and from north to south in the mountains.
• Central parts of India and northern parts of southern Peninsula also get winter rainfall occasionally.
• Arunachal Pradesh and Assam in the northeastern parts of India also have rains between 25 mm and 50 mm during these winter months.
• During October and November, northeast monsoon while crossing over the Bay of Bengal, picks up moisture and causes torrential rainfall over the Tamil Nadu coast, southern Andhra Pradesh, southeast Karnataka and south east Kerala.
The Hot Weather Season
• With the apparent northward movement of the sun towards the Tropic of Cancer in March, temperatures start rising in north India.
• April, May and June are the months of summer in north India. In most parts of India, temperatures recorded are between 30°-32°C.
• In March, the highest day temperature of about 38°C occurs in the Deccan Plateau while in April, temperature ranging between 38°C and 43°C are found in Gujarat and Madhya Pradesh.
• In May, the heat belt moves further north, and in the north-western part of India, temperatures around 48°C are not uncommon.
• Temperatures remain between 26°C and 32°C. Due to altitude, the temperatures in the hills of Western Ghats remain below 25°C.
Pressure and Winds:
• The summer months are a period of excessive heat and falling air pressure in the northern half of the country.
• Roughly, this elongated low pressure monsoon trough extends over the Thar desert in the northwest to Patna and Chotanagpur plateau in the east-southeast.
• The location of the ITCZ attracts a surface circulation of the winds which are southwesterly on the west coast as well as along the coast of West Bengal and Bangladesh.
• They are easterly or southeasterly over north Bengal and Bihar.
• In the heart of the ITCZ in the northwest, the dry and hot winds known as ‘Loo’, blow in the afternoon, and very often, they continue to well into midnight.
• Dust storms in the evening are very common during May in Punjab, Haryana, Eastern Rajasthan and Uttar Pradesh.
• These temporary storms bring a welcome respite from the oppressing heat since they bring with them light rains and a pleasant cool breeze.
• Occasionally, the moisture-laden winds are attracted towards the periphery of the trough.
• A sudden contact between dry and moist air masses gives rise to local storms of great intensity.
• These local storms are associated with violent winds, torrential rains and even hailstorms.
Some Famous Local Storms of Hot Weather Season
• Mango Shower: Towards the end of summer, there are pre-monsoon showers which are a common phenomena in Kerala and coastal areas of Karnataka. Locally, they are known as mango showers since they help in the early ripening of mangoes.
• Blossom Shower: With this shower, coffee flowers blossom in Kerala and nearby areas.
• Norwesters: These are dreaded evening thunderstorms in Bengal and Assam. Their notorious nature can be understood from the local nomenclature of ‘Kalbaisakhi’, a calamity of the month of Baisakh.
• These showers are useful for tea, jute and rice cultivation. In Assam, these storms are known as “Bardoli Chheerha”.
• Loo: Hot, dry and oppressing winds blowing in the Northern plains from Punjab to Bihar with higher intensity between Delhi and Patna.
The Southwest Monsoon Season
• Due to high temperature there is lo to attract the trade winds of Southern Hemisphere coming from the Indian Ocean.
• These southeast trade winds cross the equator and enter the Bay of Bengal and the Arabian Sea,.
• After crossing the equator, they follow a southwesterly direction. That is why they are known as southwest monsoons.
• The rain in the southwest monsoon season begins rather abruptly. One result of the first rain is that it brings down the temperature substantially.
• This sudden onset of the moisture-laden winds associated with violent thunder and lightning, is often termed as the “break” or “burst” of the monsoons.
The monsoon approaches the landmass in two branches: (i) The Arabian Sea branch (ii) The Bay of Bengal branch
Monsoon Winds of the Arabian Sea
The monsoon winds originating over the Arabian Sea further split into three branches:
(i) Its one branch is obstructed by the Western Ghats. These winds climb the slopes of the Western Ghats from 900-1200 m. Soon, they become cool, and as a result, the windward side of the Sahyadris and Western Coastal Plain receive very heavy rainfall ranging between 250 cm and 400 cm. After crossing the Western Ghats, these winds descend and get heated up. (ii) Another branch of the Arabian sea monsoon strikes the coast north of Mumbai. Moving along the Narmada and Tapi river valleys, these winds cause rainfall in extensive areas of central India. The Chotanagpur plateau gets 15 cm rainfall from this part of the branch. Thereafter, they enter the Ganga plains and mingle with the Bay of Bengal branch.
(iii) A third branch of this monsoon wind strikes the Saurashtra Peninsula and the Kachchh. It then passes over west Rajasthan and along the Aravalis, causing only a scanty rainfall. In Punjab and Haryana, it too joins the Bay of Bengal branch. These two branches, reinforced by each other, cause rains in the western Himalayas.
Monsoon Winds of the Bay of Bengal
• The Bay of Bengal branch strikes the coast of Myanmar and part of south east Bangladesh. But the Arakan Hills along the coast of Myanmar deflect a big portion of this branch towards the Indian subcontinent.
• The monsoon, therefore, enters West Bengal and Bangladesh from south and southeast instead of from the south-westerly direction. From here, this branch splits into two under the influence of the Himalayas and the thermal low is northwest India.
• Its one branch moves westward along the Ganga plains reaching as far as the Punjab plains. The other branch moves up the Brahmaputra valley in the north and the northeast, causing widespread rains. Its sub-branch strikes the Garo and Khasi hills of Meghalaya. Mawsynram, located on the crest of Khasi hills, receives the highest average annual rainfall in the world.
• Here it is important to know why the Tamil Nadu coast remains dry during this season.
There are two factors responsible for it: (i) The Tamil Nadu coast is situated parallel to the Bay of Bengal branch of southwest monsoon. (ii) It lies in the rain shadow area of the Arabian Sea branch of the south-west monsoon.
Characteristics of Monsoonal Rainfall
• Rainfall received from the southwest monsoons is seasonal in character, which occurs between June and September.
• Monsoonal rainfall is largely governed by relief or topography. For instance the windward side of the Western Ghats register a rainfall of over 250 cm. Again, the heavy rainfall in the north -eastern states can be attributed to their hill ranges and the Eastern Himalayas.
• The monsoon rainfall has a declining trend with increasing distance from the sea. Kolkata receives 119 cm during the southwest monsoon period, Patna 105 cm, Allahabad 76 cm and Delhi 56 cm.
• The monsoon rains occur in wet spells of few days duration at a time. The wet spells are interspersed with rainless, interval known as ‘breaks’. These breaks in rainfall are related to the cyclonic depressions mainly formed at the head of the Bay of Bengal, and their crossing into the mainland. Besides the frequency and intensity of these depressions, the passage followed by them determines the spatial distribution of rainfall.
• The summer rainfall comes in a heavy downpour leading to considerable run off and soil erosion.
• Monsoons play a pivotal role in the agrarian economy of India because over three-fourths of the total rain in the country is received during the southwest monsoon season.
• Its spatial distribution is also uneven which ranges from 12 cm to more than 250 cm.
• The beginning of the rains sometimes is considerably delayed over the whole or a part of the country.
• The rains sometimes end considerably earlier than usual, causing great damage to standing crops and making the sowing of winter crops difficult.
Season of Retreating Monsoon
• October and November are known for retreating monsoons.
• By the end of September, the southwest monsoon becomes weak as the low pressure trough of the Ganga plain starts moving southward in response to the southward march of the sun.
• The monsoon retreats from the western Rajasthan by the first week of September.
• It withdraws from Rajasthan, Gujarat, Western Ganga plain and the Central Highlands by the end of the month.
• By the beginning of October, the low pressure covers northern parts of the Bay of Bengal and by early November, it moves over Karnataka and Tamil Nadu.
• By the middle of December, the centre of low pressure is completely removed from the Peninsula.
• The retreating southwest monsoon season is marked by clear skies and rise in temperature.
• The land is still moist. Owing to the conditions of high temperature and humidity, the weather becomes rather oppressive. This is commonly known as the ‘October heat’. Here, October and November are the rainiest months of the year.
• The widespread rain in this season is associated with the passage of cyclonic depressions which originate over the Andaman Sea and manage to cross the eastern coast of the southern Peninsula.
Traditional Indian Seasons
Seasons
Months (According to the Indian Calendar)
Months (According to the Indian Calendar)
Vasanta
Chaitra-Vaisakha
March-April
Grishma
Jyaistha-Asadha
May-June
Varsha
Sravana-Bhadra
July-August
Sharada
Asvina-Kartika
September-October
Hemanta
Margashirsa-Pausa
November-December
Shishira
Magha-phalguna
January-February
Distribution of Rainfall
The average annual rainfall in India is about 125 cm, but it has great spatial variations.
• Areas of High Rainfall : The highest rainfall occurs along the west coast, on the Western Ghats, as well as in the sub-Himalayan areas is the northeast and the hills of Meghalaya. Here the rainfall exceeds 200 cm. In some parts of Khasi and Jaintia hills, the rainfall exceeds 1,000 cm. In the Brahmaputra valley and the adjoining hills, the rainfall is less then 200 cm.
• Areas of Medium Rainfall : Rainfall between 100-200 cm is received in the southern parts of Gujarat, east Tamil Nadu, northeastern Peninsula covering Odisha, Jharkhand, Bihar, eastern Madhya Pradesh, northern Ganga plain along the sub-Himalayas and the Cachar Valley and Manipur.
• Areas of Low Rainfall : Western Uttar Pradesh, Delhi, Haryana, Punjab, Jammu and Kashmir, eastern Rajasthan, Gujarat and Deccan Plateau receive rainfall between 50-100 cm.
• Areas of Inadequate Rainfall: Parts of the Peninsula, especially in Andhra Pradesh, Karnataka and Maharashtra, Ladakh and most of western Rajasthan receive rainfall below 50 cm.Snowfall is restricted to the Himalayan region.
Climatic Regions of India
Major climatic types of India based on Koeppen‘s scheme: Koeppen based his scheme of Climatic classification on monthly values of temperature and precipitation. He identified five major climatic types, namely:
(i) Tropical climates, where mean monthly temperature throughout the year is over 18°C.
(ii) Dry climates, where precipitation is very low in comparison to temperature, and hence, dry. If dryness is less, it is semi arid (S); if it is more, the climate is arid(W).
(iii) Warm temperate climates, where mean temperature of the coldest month is between 18°C and minus 3°C.
(iv) Cool temperate climates, where mean temperature of the warmest month is over 10°C, and mean temperature of the coldest month is under minus 3°C.
(v) Ice climates, where mean temperature of the warmest month is under 10°C.
