NCERT MOST IMPORTANT QUESTIONS CLASS – 11 | GEOGRAPHY | CHAPTER- 5 | MINERALS AND ROCKS | EDUGROWN |

In This Post we are  providing  CHAPTER 5 MINERALS AND ROCKS NCERT MOST IMPORTANT QUESTION for Class 11 GEOGRAPHY which will be beneficial for students. These solutions are updated according to 2021-22 syllabus. These MCQS  can be really helpful in the preparation of Board exams and will provide you with a brief knowledge of the chapter.

NCERT MOST IMPORTANT QUESTION ON MINERALS AND ROCKS

Question 1.
What is lithification?
Answer:
The fragments of the rocks are transported by various exogenous agencies and deposited. These deposits through compaction and/or cementation turn into rocks. This process is called lithification. In many sedimentary rocks, the layers of deposits. retain their characteristics even after lithification.

Question 2.
How would you classify the igneous rocks based on the size and nature of crystals?
Answer:
There are five types of igneous rocks based on the size and nature of crystals viz.

1. rocks with phaneritic textured crystals
2. rocks with orphan textured crystals
3. equigranular textured rocks, and
4. porphyritic textured rocks.

The crystals large enough to be seen with naked eyes or with the help of hand lens are called phaneritic textured crystals, whereas those too small to be distinguished without the aid of a microscope are – called orphan textured crystals of the igneous rocks. Where crystals in the rocks are all within the same size range, the texture is described as equigranular, whereas few large crystals are embedded in a matrix of smaller crystals, the texture is porphyritic.

Question 3.
Discuss the classification of sedimentary rocks into clastic and non-clastic division.
Answer:
Clastic means ‘broken’, describes clastic sediments consisting of particles removed individually from a parent rock source. The naming of clastic rocks depends on the size of component mineral grains.

The non-clastic sedimentary rocks are made of sediments of two basic types: chemical precipitates and organically derived sediments.

The chemical precipitates are solid mineral matters precipitated from an aqueous solution. The rock salt and gypsum are its examples. The organically derived sediments consist of remains of plants and animals as well as mineral matters produced by activities of plants and animals. Coal and limestone are examples.

Question 4.
What are schists?
Answer:
As metamorphism continues a large percentage of the minerals assume the plate-like shape and are assembled in parallel orientation in the rock, a structure is known as foliation. Strongly developed foliation is known as schist.

Question 5.
What is meant by mineral hardness?
Answer:
The degree to which a mineral surface resists being scratched is known as its mineral hardness. Hardness is important because it determines how a mineral is worn away by the abrasive action of stream, waves, wind and glaciers in the processes of erosion and transportation..

Question 6.
Write short notes on:
1. Sedimentary rocks
2. Types of metamorphism
Answer:
1. Sedimentary rocks: Exogenous agencies such as rain, wind, ice, running water, plants and animals are constantly hurried in rock disintegration producing loose and broken rock fragments in all sizes. These minerals are carried by wind, ice and running water in depressions such as lakes and seas on the earth’s surface. Such dropped materials are called sediments. Accumulation of these sediments in course of time gives rise to sedimentary rocks. The word ‘sedimentary’ is derived from the Latin word ‘sedimented’ means setting down. The sediments are usually deposited in distinct layers or strata. Therefore, these rocks are also known as stratified rocks.

2. Types of metamorphism: Metamorphism is the process of transformation of pre-existing rock into a new rock. Thus, metamorphic rocks are found when a rock is subjected to heat and/or pressure. Their characteristics are altered by forming new mineral forms. There are three types of metamorphism, viz. foliation, lineation and banding. When, under continued metamorphism, its minerals assume the plate-like shape and are assembled in parallel orientation in the rock, it is called foliation, e.g., Schist is formed in this manner.

When the mineral grains are drawn out into long, thin, pencil-like objects, all in parallel alignment, it is referred to as lineation. In another type of metamorphism, i.e., banding, the minerals of different varieties or groups are segregated into alternate layers. These layers are usually of light or dark shades, making the banding conspicuous.

Question 7.
What is the economic importance of minerals?
Answer:
Mineral resources can be divided into four main groups – essential resources, energy resources, metal resources and industrial resources. The most basic group, essential resources, comprises soil and water. Energy resources can be divided into fossil fuels (crude oil, natural gas, coal, oil shale and tar sand) and nuclear fuels (uranium, thorium and geothermal power). Metal resources range from structural metals such as iron, aluminium and titanium to ornamental and industrial metals such as gold, platinum and gallium.

Mineral deposits have two geological characteristics that make them a real challenge to modem civilization. First, all of them are non-renewable resources. The geological processes that form them are much slower than the rate at which we exploit them. There is no likelihood of our ability to grow mineral deposits at a rate equal to our consumption. Second, mineral deposits have a place value. We cannot decide from where to extract them; nature made that decision for us when the deposits were formed.

Question 8.
Describe the categorization of metamorphic rocks.
Answer:
The metamorphic rocks can be broadly grouped into two major classes – cataclastic rocks and recrystallised rocks. Cataclastic rocks are formed by mechanical disruption (breaking and crushing) of the original materials. The process is described as dynamic metamorphism.

The recrystallised rocks are further divided into two sub-classes – contact and regional metamorphic rocks. The contact metamorphic rocks are formed by recrystallisation under high temperature caused by intruding magma. The rocks are not subjected to bending or breaking and new minerals emanating from magma are added to metamorphosed rocks. The regional metamorphic rocks undergo recrystallisation during the process of being deformed by sharing often under the condition of high pressure or high temperature or bolts.

Question 9.
Discuss various types of rocks in detail.
Answer:
There are three main groups of rocks: igneous, sedimentary and metamorphic rocks.
Igneous rocks: These are formed from lava hurled out of a volcano or from the cooling of hot magma below the crust. Granite is a coarse-grained rock that was formed by the slow cooling of magma. Basalt is a fine-grained igneous rock, almost black, that was formed by quick cooling of lava. Chemical differentiation of magma gives rise to mafic and felsic types of igneous rocks.

The size of mineral crystals in an igneous rock largely depends upon the rate of cooling of magma. As a general rule, rapid cooling results in small crystals and slow cooling in large crystals. Extremely sudden cooling results in the formation of a natural glass which is non-crystalline. Large bodies of magma trapped beneath the surface cool very slowly because the surrounding rocks conduct the heat slowly. Rapid cooling occurs in lava that loses heat rapidly to the atmosphere or to the overlying ocean water.

Question 10.
Describe the formation of igneous rocks, giving suitable examples of various types.
Answer:
The igneous rocks are divided into extrusive rocks and intrusive rocks. When the magma solidifies on the surface of the earth, we call it an extrusive rock. A typical example of this kind of rock is basalt. It is a very fine-grained rock, usually Sf black in colour.

On the other hand, when the magma solidifies in the crust, below the surface, it is called an intrusive rock. The few most common examples of intrusive rocks are granite and dolerite. More frequent, however, is the solidification of magma below the earth’s surface leading to the formation of intrusive rocks. Igneous rocks are classified on the basis of chemical composition and texture. Chemical differentiation of magma gives rise to mafic and felsic types of igneous rocks.

Texture relates to the sizes and pattern of the mineral crystals present in the rock. The size of mineral crystals in an igneous rock depends largely upon the rate of cooling of magma. As a general rule, rapid cooling results in small crystals and slow cooling results in large crystals. Extremely sudden cooling results in the formation of natural glass which is non-crystalline. Large bodies of magma trapped beneath the surface cool very slowly because the surrounding rocks conduct the heat slowly. Rapid cooling occurs in lava that loses heat rapidly to the atmosphere or to the overlying ocean water.