Question 1

Question 5What is Metamorphism? What are its causes?

Accepted Answer

Alteration of the minerals and textures of a rock by changes in temperature and pressure and by a gain or loss of chemical components to such an extent that the diagnostic features of the original rocks are modified is called metamorphism.Following are the causes of metamorphism:volcanic eruptionsthe mountain building movementsendogenetic forcescontact with undergoing water

Question 2

Question 6Name a few important characteristics of Sedimentary Rocks.

Accepted Answer

A few important characteristics of Sedimentary Rocks are:The material of sedimentary rock is derived from other pre-existing rocks.They are layered rocks.Sediments are deposited in sequential order i.e. size of sediments decrease from littoral margins to the centre of the water bodies.Most of the sedimentary rocks are permeable and porous.They contain fossils.

Question 3

Question 7Name the various types of Metamorphic Rocks.

Accepted Answer

The various types of metamorphic rocks are slate, schist, gneiss, quartzite, marble, amphibolite, meta-conglomerate and hornfel.

Question 4

Question 8Name the agents involved in the formation of sedimentary rocks.

Accepted Answer

The agents involved in the formation of sedimentary rocks are rivers, lakes, sea, glaciers, wind and organic materials. The processes of erosion, weathering, dissolution and lithification lead to formation of sedimentary rocks.

Question 5

Question 9Give examples of metamorphic rocks formed from igneous and sedimentary rocks.

Accepted Answer

Metamorphic rocks formed from igneous rocks — Gniess from granite, Schist from BasaltMetamorphic rocks formed from sedimentary rocks — Marble from limestone, Quartzite from Sandstone.

Question 6

Question 10What are Sills and Dykes?

Accepted Answer

Sills— It is sheet like body of igneous rock. It is formed when magma forces its way between two layers of sedimentary rocks and cools and solidifies there.Dykes— It is sheet like body of intrusive igneous rock. When magma is forced upwards, it fills vertical cracks or fissures in existing rock and it hardens there to form dykes.

Question 7

Question 11Why are sedimentary rocks also called stratified rocks?

Accepted Answer

Sedimentary rocks are formed by deposition of sediments in layers in beds of water bodies or on earth's surface (if brought by wind). They are deposited in layers, therefore, they are known as stratified rocks and layers are called strata.

Question 8

Question 12What processes are involved in the formation of igneous rocks?

Accepted Answer

The processes involved in the formation of igneous rocks are cooling, solidification and crystallization.

Question 9

Question 13What is a Rock Cycle?

Accepted Answer

A cyclic process of changing the form of rocks is called Rock cycle. It represents the interrelationships among the three rock-forming processes: igneous, sedimentary and metamorphic.

Question 10

Question 14What are the rocks?

Accepted Answer

An assemblage of minerals bound together that form a more or less definite unit of the Earth's crust is called rocks.

Question 11

Question 15Classify the rocks on the basis of their origin.

Accepted Answer

On the basis of their origin, rocks are of three types:Igneous rocksSedimentary rocksMetamorphic rocks

Question 12

Question 16What is meant by intrusive rocks?

Accepted Answer

Magma that solidifies below the Earth's surface and remains surrounded by the pre-existing rock is called intrusive rocks. For example, granite.

Question 13

Question 17What are extrusive rocks?

Accepted Answer

The rocks that are formed due to solidification of magma on the Earth's surface are called Extrusive Igneous Rocks. For example, Obsidian.

Question 14

Question 18How important are rocks for industrial development?

Accepted Answer

The importance of rocks in industrial development are:Rocks contain minerals called ores which are used for extracting metals and non-metals.They provide fossil fuels like coal and petroleum.The entire automobile industry uses petrol for their transport system.They provide raw material for manufacturing industries like limestone and gypsum are needed by cement industry.They are used as building materials. For example, granite and marble.

Question 15

Question 1Rocks and Minerals

Accepted Answer

S.No.RocksMinerals1.Rocks are aggregates of mineral elements.Minerals are naturally occuring solid inorganic substances.2.Rocks are heterogeneous in their composition.Minerals are homogeneous in form.3.A rock has no definite chemical composition.Minerals have a definite chemical composition.4.On the basis of origin, rocks are igneous, sedimentary and metamorphic.Four chief mineral groups are silicates, carbonates, sulphides and metallic minerals.5.Other important types of rocks are basalt, granite, sandstone, slate and quartz.Other important minerals are iron, silicon, magnesium, nickel, calcium, potassium, etc.

Question 16

Question 2Volcanic rocks and plutonic rocks

Accepted Answer

S.No.Volcanic rocksPlutonic rocks1.They are also called extrusive rocks.They are also called intrusive rocks.2.They are formed when magma solidifies on the surface of earth.They are formed when magma solidifies within the earth's crust.3.They are smooth, crystalline and fine grained.They are coarse textured, hard rocks with large crystals.4.For example- basaltFor example- granite

Question 17

Question 3Thermal and Dynamic Metamorphism

Accepted Answer

S.No.Thermal MetamorphismDynamic Metamorphism1.It occurs when rocks are formed due to high temperature.It occurs when rocks are formed due to high pressure.2.For example- slate is formed from clay.For example- marbles are formed from Dolomites.

Question 18

Question 4Lithosphere is called rocksphere.

Accepted Answer

The Lithosphere is the outermost layer of the Earth's crust that is made up of solid rocks, including igneous and sedimentary rocks. In Greek, Litho means rock or stone. Thus, Lithosphere is also called rocksphere.

Rocks and Rock Cycle

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