*The earth

The earth made up of rocks. Because of suitable conditions on the outer surface, we live on it. This outer surface is called crust.

But the conditions change as we go deep into the earth. A layer of molten rocks is found under the crust. This is called mantle. The centre of the earth is the hottest part. This called core, which is made up of molten metals.

You might have studied volcanoes that emit lava causing great destruction. Volcanoes are caused due t holes or cracks in the earth’s crust. Molten rock called magma, Comes out from the mantel of the earth to the surface of earth through these cracks or holes. The magma flowing out is called Lava. This red hot liquid cools to form rocks.

*Formation of earth

It is believed that billions years ago, the sun and all the planets were the moving clouds of hot gases and dust. The matter gases condensed to form the sun, earth and other planets. After the formation of the earth, it took million years to cool the outer surface of the earth.

*Earth –movement

The earth is always moving. It spins around its own axis and it revolves around the sun.

*Rotation of earth

Look carefully the rotating top. You will find it is spinning around the line passing through its centre. In the same way, the earth is also spinning around an imaginary line passing through north and South Pole. This imaginary line is called axis of rotation. The spinning of the earth is called rotation.

One rotation of the earth is completed in 24 hours. Days and nights are caused due to the rotation of the earth.

The earth revolves around the sun

Earth revolves around the sun in a fixed path known as orbit. Such movement of earth is called revolution. The earth completes its one revolution in 365 days or one year.

Seasons

Weather changes after few months. Summers are very hot and winters are extremely cold. Summer days are longer than winter days. Seasons occur due to the revolution of the earth.

Earth is divided into two equal halves by an imaginary line. These halves are called northern hemisphere and southern hemisphere. The imaginary line is known as Equator. India lines in northern hemisphere.

Earth is in tilted position when it revolves around the sun. The northern hemisphere receives more sunlight and has summer when North Pole is titled towards the sun. During same period, South Pole is away from sun. So southern hemisphere gets less sunlight and had winter.

After a few months, the position of the earth changes, north poles goes away from the sun and South Pole tilts towards the sun. This change in the earth’s position causes seasons.