NCERT Solutions Class 7th Geography Social Science Chapter – 2 Inside Our Earth Notes

May 11, 2022

NCERT Solutions Class 7th Geography Social Science Chapter – 2 Inside Our Earth

Textbook	NCERT
Class	7^th
Subject	(Geography)Social Science
Chapter	Chapter – 2
Chapter Name	Inside Our Earth
Category	Class 7th Social Science Geography
Medium	English
Source	Last Doubt

NCERT Solutions Class 7th Geography Social Science Chapter – 2 Inside Our Earth Notes What is inside in our earth?What is the earth ? What can we learn from inside our earth? Where are we inside Earth? How old is our Earth? How old is the Earth kids? How old is Earth born? What age is Earth? Is the Earth 1000 years old? What is the first life on Earth? When was Earth first called? Who named Earth? What is Earth’s real name? Who gave Earth its name? How big is Earth? How did Earth get water? Does Earth have a symbol? What is our Sun called? What are 5 facts about Earth? What is Earth made of? What is rock ? What is lava ? How deep is Earth?

NCERT Solutions Class 7th Geography Social Science Chapter – 2 Inside Our Earth

Chapter – 2

Inside Our Earth

Notes

Interior of the Earth

The Earth is made up of several concentric layers with one inside another. The uppermost layer over the earth’s surface is called the crust. It is the thinnest of all the layers. It is about 35 km on the continental masses and only 5 km on the ocean floors. The main mineral constituents of the continental mass are silica and alumina. It is thus called sial (si-silica and al-alumina). The oceanic crust mainly consists of silica and magnesium; it is therefore called sima (si-silica and ma-magnesium).
• Mantle is just beneath the crust, which extends up to a depth of 2900 km below the crust. The innermost layer is the core with a radius of about 3500 km. It is mainly made up of nickel and iron and is called nife (ni – nickel and fe – ferrous i.e. iron). The central core has a very high temperature and pressure.

Rock

Any natural mass of mineral matter that makes up the earth’s crust is called a rock. It can be of different colour, size and texture. There are three major types of rocks:

Rocks and Minerals

The earth’s crust is made up of various types of rocks.

Igneous rocks

When the molten magma cools, it becomes solid. Rocks thus formed are called igneous rocks or primary rocks. There are two types of igneous rocks: intrusive rocks and extrusive rocks.

Extrusive igneous rocks

When molten lava comes on the earth’s surface, it rapidly cools down and becomes solid. Rocks formed in such a way on the crust are called extrusive igneous rocks. For example, basalt. The Deccan plateau is made up of basalt rocks.

Intrusive igneous rocks

Sometimes the molten magma cools down deep inside the earth’s crust. Solid rocks so formed are called intrusive igneous rocks. Granite is an example of such a rock. Grinding stones used to prepare paste/powder of spices and grains are made of granite.

Sedimentary Rocks

Rocks roll down, crack, and hit each other and are broken down into small fragments called sediments. These sediments are transported and deposited by wind, water, etc. These loose sediments are compressed and hardened to form layers of rocks. These types of rocks are called sedimentary rocks. For example, sandstone is made from grains of sand.

Igneous and sedimentary rocks can change into metamorphic rocks under great heat and pressure. For example, clay changes into slate and limestone into marble.

Rock cycle

The process of transformation of the rock from one to another is known as the rock cycle.

When the igneous and sedimentary rocks are subjected to heat and pressure they change into metamorphic rocks. The metamorphic rocks, which are still under great heat and pressure meltdown to form molten magma. This molten magma again can cool down and solidify into igneous rocks

Rocks are made up of different minerals. Minerals are naturally occurring substances which have certain physical properties and definite chemical composition. For example, coal, natural gas and petroleum. They are also used in industries – iron, aluminium, gold, uranium, etc, in medicine, in fertilisers, etc.