Minerals and rocks

Class 11 | Geography | Chapter 5 | Questions and Answers | NCERT

1. Multiple choice questions

(i) Which one of the following are the two main constituents of granite?

(a) Iron and Nickel

(b) Iron and Silver

(c) Silica and Aluminium

(d) Iron oxide and Potassium

(ii) Which one of the following is the salient feature of metamorphic rocks?

(a) Changeable

(b) Quite

(c) Crystalline

(d) Foliation

(iii) Which one of the following is not a single element mineral?

(a) Gold

(b) Silver

(c) Mica

(d) Graphite

(iv) Which one of the following is the hardest mineral?

(a) Topaz

(b) Diamond

(c) Quartz

(d) Feldspar

(v) Which one of the following is not a sedimentary rock?

(a) Tillite

(b) Borax

(c) Breccia

(d) Marble

2. Answer the following questions in about 30 words.

(i) What do you mean by rocks? Name the three major classes of rocks?

A rock is an aggregate of one or more minerals. The earth’s crust is composed of rocks.

The three major classes of rocks are –

• Igneous rocks
• Sedimentary rocks
• Metamorphic rocks

(ii) What is an igneous rock? Describe the method of formation and characteristics of igneous rock.

Igneous rocks form through the processes of cooling and solidification of magma and lava. When magma in its upward movement cools and turns into solid form it is called igneous rock. The process of cooling and solidification can happen in the earth’s crust or on its surface.

Characteristics of Igneous rocks:

• Igneous rocks do not include fossils.
• They are extremely hard in nature.
• They consist of crystals.

(iii) What is meant by sedimentary rock? Describe the mode of formation of sedimentary rock.

Sedimentary rocks are those rocks that are formed by the accumulation of sediments by agents of denudation such as wind, river and sea waves. These accumulations gradually turn into rocks.

Rocks of the earth’s surface are exposed to denudational agents and are broken up into fragments of various sizes. Such fragments are transported by various exogenous agencies and deposited which convert them into rocks through compaction. This process is called lithification.

(iv) What relationship explained by rock cycle between the major type of rock?

Rock cycle is a continuous process through which old rocks are transformed into new ones.

• Igneous rocks are primary rocks and other rocks (sedimentary and metamorphic) form from these primary rocks.
• Igneous rocks can be changed into sedimentary rocks or metamorphic rocks.
• The fragments derived out of igneous and metamorphic rocks form into sedimentary rocks.
• Sedimentary rock can change into metamorphic rock or into igneous rock.
• Metamorphic rock can change into igneous rock or into sedimentary rock.