Inside the Earth
Inside the Earth
The Earth, our home, is always changing. These changes happen both on the outside and deep inside. Have you ever thought about what is inside the Earth? What is it made of?
The Earth is made up of different layers, like the layers of an onion. These layers are one inside the other.
1. Crust
The crust is the top layer of the Earth where we live. It is the thinnest layer.
It is about 35 kilometers thick on land.
It is only about 5 kilometers thick under the oceans.
The crust on land is mostly made of silica and alumina, so it is called sial (si for silica and al for alumina).
The crust under the ocean has silica and magnesium, so it is called sima (si for silica and ma for magnesium).
2. Mantle
The mantle is the layer just below the crust. It goes down to about 2900 kilometers deep. It is made of hot, thick rock.
3. Core
The core is the deepest and hottest part of the Earth. It is about 3500 kilometers deep. It is made of nickel and iron, so it is called nife (ni for nickel and fe for iron).
The core has very high temperature and pressure.
Rocks and Minerals
The Earth’s outer layer (called the crust) is made of rocks.
A rock is a natural thing made of one or more minerals.
Rocks can be of different colors, sizes, and shapes.
Three Main Types of Rocks
1. Igneous Rocks
l These rocks form when hot melted rock (called magma) cools and becomes hard.
l Magma that comes out of a volcano is called lava.
l If lava cools on the Earth’s surface, it makes extrusive igneous rocks.
Example: Basalt
l If magma cools inside the Earth, it makes intrusive igneous rocks.
Example: Granite
2. Sedimentary Rocks
l Wind and water break rocks into small pieces called sediments.
l These sediments pile up in layers.
l Over time, they get pressed together and become sedimentary rocks.
Example: Sandstone
l Sometimes, they have fossils (old remains of plants or animals).
3. Metamorphic Rocks
When igneous or sedimentary rocks get very hot and are under high pressure, they change into metamorphic rocks.
Examples: Clay becomes slate , Limestone becomes marble
Rock Cycle
Rocks can change from one type to another in a circle:
1. Magma cools → makes igneous rocks
2. Igneous rocks break into pieces → become sediments
3. Sediments press together → form sedimentary rocks
4. Heat and pressure change them → into metamorphic rocks
5. Metamorphic rocks melt → become magma
6. The cycle starts again
Minerals
l Minerals are natural materials found in rocks.
l They have special colors, shapes, and chemicals.
l Minerals are very useful:
l Coal, gas, and oil – give us energy
l Iron, gold, aluminium – used in factories
l Some minerals – used in medicines and fertilizers
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Fun Fact - Many games use stones, like:
Seven stones (pitthoo)
Hopscotch (stapu)
Five stones (gitti)
Ask your parents or grandparents—they may know more!
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