Ch-2 Inside our earth class 7 ncert

Ch-2 Inside our earth class 7 Ncert

I hope you will enjoy the lesson

Inside Our Earth

The earth, is a dynamic planet. It is constantly undergoing changes inside and outside.

Interior of the Earth

The earth is made up of several concentric layers with one inside another. Crust – The uppermost layer over the earth’s surface. 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 si-al (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 – Just beneath the crust is the mantle which extends up to a depth of 2900 km. Core – 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.

Rocks and Minerals

The earth’s crust is made up of various types of rocks. Rock- Any natural mass of mineral matter that makes up the earth’s crust. There are three major types of rocks- Igneous rocks-when the molten magma cools; it solidifies to become igneous rock. Sedimentary rocks- igneous rocks are broken down into small particles that are transported and deposited to form sedimentary rocks. Metamorphic rocks- When the igneous and sedimentary rocks are subjected to heat and pressure, they change into metamorphic rocks. Rocks are made up of different minerals. Minerals- are naturally occurring substances which have certain physical properties and definite chemical composition.

Rocks and Minerals (contd.)

Minerals are very important to humankind. Some are used as fuels. For example, coal, natural gas and petroleum. They are also used in industries – iron, aluminium, gold, uranium, etc., in medicine, in fertilisers, etc.

Thanks

I HOPE YOU UNDERSTOOD THE CHAPTER. NOW LETS HAVE SOME QUESTIONS OR A SMALL TEST.

Multiple Choice

The Tajmahal is made of which one of these rocks?

• Sandstone

• Marble

• Granite

• Basalt

Multiple Choice

The core is made up of

• Silica and magnesium

• Nickel and iron

• Coal and marble

• Silica and alumina

Multiple Choice

Gold, petroleum and coal are examples of

• Rocks

• Minerals

• Fossils

• None of these

Multiple Choice

The core has a radius of about

• 3100 km

• 3300 km

• 3500 km

• 2900 km

Multiple Choice

The Deccan plateau is mainly made up of

• Basalt rocks

• Sandstone

• Marble

• Granite

Multiple Choice

The oceanic crust mainly consists of which of these minerals

• Silica and alumina

• Silica and magnesium

• Nickel and iron

• None of these

Multiple Choice

Marble is a type of ___________ rock

• metamorphic

• igneous

• expensive

• sedimentary

Multiple Choice

The fossil fuels are found in ____________ rocks

• igneous

• sedimentary

• metamorphic

• volcanic

Multiple Choice

The rocks which are formed from molten magma are called ____________ rocks

• igneous

• sedimentary

• metamorphic

• metallic

Multiple Choice

Granite, Chalk, clay and salt are examples of ___________

• rocks

• minerals

• fossils

• metals

Multiple Choice

The thinnest layer of the earth is the..

• mantle

• outer core

• crust

• inner core

Multiple Choice

Which of the following is a sedimentary rock?

• Granite

• Obsidian

• Limestone

• Marble

Multiple Choice

Which one of the following called as primary rocks?

• Metamorphic rocks

• Igneous rocks

• sedimentary rocks

• Hard rocks

Multiple Choice

Sedimentary is a word derived from _____ word ______

• Greek, sedentum

• Latin, sedentum

• French, Sedimenta

• Spanish, Sedenta

Multiple Select

Igneous is a _____ word meaning ______

• Latin, fire

• Greek, Stones

• French, Water

• Latin, Hot air

Multiple Select

Three major types of rocks:

• igneous

• sedimentary

• metamorphic

• sial

• sima

Multiple Choice

The uppermost layer over the earth’s surface is called :

• Crust

• Mantle

• Core

THANKS

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