GEOGRAPHY

INSIDE OUR EARTH.

earth

Just like an onion, the earth is made up of several concentric layers with one inside another 

earth

The earth comprises three layers: crust, mantle and core. Constant changes take place inside as well as outside the earth.

crust

The uppermost layer over the earth’s surface is called the crust. It is about 35 km thick on the continental masses and only 5 km thick on the ocean floor. It is made up of silica and alumina and thus called sial.

crust

The oceanic crust mainly consists of silica and magnesium called sima. Just below the crust is the mantle up to an extent of 2,900 km.

Crust: The uppermost layer over the earth’s surface. It is very thin.

core

The innermost layer is the core with a radius of 3,500 km. As it is made of nickel and iron, it is called nife(ni-nickel and fe-ferrous i.e. iron). The central core has a very high temperature and pressure.

rocks

Rock: A rock is a natural mass of mineral matter that makes up the earth’s crust.

Igneous rock: 

These rocks are formed by cooling and solidifying molten magma.

TYPES OF IGNEOUS ROCKS

Extrusive igneous rock

Intrusive igneous rock

Extrusive igneous rock

 When the molten lava comes on the earth’s surface, it rapidly cools down and becomes solid. Rocks formed in this way on the crust are called extrusive igneous rocks.

Intrusive igneous rock

When the molten magma cools down deep inside the earth’s crust solid intrusive igneous rocks are formed.

Sedimentary rock: 

When loose sediments are compressed and hardened, layers of rocks are formed. These types of rocks are known as sedimentary rocks.

now it is quiz time revise all slides and solve it correct

thankyou

by: vamshi

Multiple Choice

The upper most layer of the earth’s surface is called

• (a) the crust

• (b) the brust

• (c) the roads

Multiple Choice

Core is the innermost layer of the earth.

• true

• false

Multiple Choice

Mantle extends up to the depth of 2900 km.

• true

• false

Multiple Choice

Crust is the thickest of all the layers.

• true

• false