1. Consider the following statements: a. Pusuant to the report of H.N. Sanyal Committee, the contempt of Courts Act, 1971 was passed. b. The Constitution of India empowers the Supreme Court and the High Courts to punish for contempt of themselves. c. The Constitution of India defines Civil Contempt and Criminal Contempt. d. In India, the Parliament is vested with powers to make laws on Contempt of Court. Which of the statements given above is/are correct? 1. a and b only 2. a, b and d 3. c and d only 4. 3 only Ans - 2 2. Consider the following statements: a. A bill amending the Constitution requires a prior recommendation of the President of India. b. When a Constitution Amendment Bill is presented to the President of India, it is obligatory for the President of India to give his/her assent. c. A Constitution Amendment Bill must be passed by both the Lok Sabha and the Rajya Sabha by a special majority and there is no provision for joint sitting. Which of the statement...
The earth's crust is composed of rocks. A rock is an aggregate of one or more minerals. Rock may be hard or soft and in varied colours. For example - granite is hard and soapstone is soft. Gabbro is black and quartzite can ve milky white. Rocks do not have definite composition of mineral constituents. Feldspar and quartz are the most common minerals found in rocks.
PETROLOGY
Petrology is science of rocks. A petrologist studies rocks in all their aspects i.e, mineral composition, texture, structure, origin, occurance, alteration and relationship with other rocks.
As there is a close relation between rocks and landforms, rocks and soils, a geographer requires basic knowledge of rocks. There are many different kinds of rocks which are grouped under three families on the basis of their mode of formation.
They are :
1. Igneous Rocks
2. Sedimentary Rocks
3. Metamorphic Rocks
IGNEOUS ROCKS
As Igneous rocks form out of magma and lava from interior of the earth, they are known as primary rocks.
The igneous rocks (Ignis - in Latin means 'Fire') are formed when magma cools and solidifies.
When magma in its upward movement cools and turns into solid form it is igneous rock.
The process of cooling and solidification can happen in the earth's crust or on the surface of the earth.
igneous rocks are classified based on texture. Texture depends upon size and arrangement of grains or other nphysical conditions of the materials. If molten material is cooled slowly at great depths, mineral grains may be very large. Sudden cooling would result in intermediate sizes of grains making up igneous rocks. Granite, gabbro, pegmatite, basalt, volcanic breccia and tuff are some examples of igneous rocks.
SEDIMENTARY ROCKS
The word 'sedimentary' is derived from the Latin word sedimentum, which means settling. Rocks ( igneous, sedimentary, and metamorphic ) of the earth's surface are exposed to denudational agents, and are broken up into various sizes of fragments. Such fragments are transported by different exogenous agencies and deposited. These deposits through compaction turn into rocks. This process is called lithification. In many sedimentary rocks, the layers of deposits retain their characteristics even after lithification. Hence we see a number of layers of varying thickness in sedimentary rocks like sandstone, shale etc.
Depending upon the mode of formation, sedimentary rocks are classified into three major groups:
1. Mechanically formed - Sandstone, conglomerate, limestone, shale, loess etc.
2. Organically formed - geyserite, chalk, limestone, coal etc.
3. Chemically formed - Chert, limestone, halite, potash etc
METAMORPHIC ROCKS
The word metamorphic means 'change of form'. These rocks form under the action of pressure, volume and temperature changes. Metamorphism occurs when rocks are forced down to lower levels by tectonic processes or when molten magma rising through the crust comes in contact with the crustal rocks or the underlying rocks are subjected to great amounts of pressure by overlying rocks. Metamorphism is a process by which already consolidated rocks undergo recrystallisation and reorganisation of materials within rocks.
Mechanical disruption and reorganisation of the original minerals within rocks due to breaking and crushing without any appreciable chemical changes is called Dynamic Metamorphism.
The materialls of rocks chemically alter and recrystallize due to thermal metamorphism.
There are two types of thermal metamorphism -
1. Contact meta-morphism
2. Regional meta-morphism
In Contact Meta-Morphism, the rocks come in contact with hot intruding magma and lava and the rock materials recrystallise under high temperatures. Quite often new materials form out of magma or lava are added to the rocks.
In Regional Meta-Morphism, the rocks undergo recrystallisation due to deformation caused by tectonic shearing together with high temperature or pressure or both.
In the process of metamorphism in some rocks grains or minerals get arranged in layers or lines. Such an arrangement of minerals or grains in metamorphic rocks is called foliation or lineation.
Sometimes minerals or materials of different groups are arranged into alternating thin to thick layers appearing in light and dark shades. Such a stucture in metarmorphic rocks is called Banding and rocks displaying banding are called banded rocks.
Types of metamorphic rocks depend upon original rocks that were subjected to metamorphism. Metamorphic rocks are classified into two major groups -
1. Foliated Rocks
2. Non-foliated Rocks
Examples of metamorphic rocks :
Gneissoid, granite, syenite, slate, schist, marble, quartzite etc.
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