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The earth and the moon
Earth
The earth is a planet has it most around the sun in a fix orbit. It also called the blue planet has it appear blue whale from the space. It is because almost 70% of the earth surface is cover with water.
The earth is a unique planet. It is the only planet, where life is known to exist in the whole universe.
Movement of earth
The earth show two kinds of movements.
1. Spin on its axis. This moment is called rotation.
➢ The rotation of the earth cause day and night.
2. It moves around the sun in a fix orbit. This moment is called revolution.
➢ The Earth takes about a year to complete one revolution.
The earth surface is made of mountain, valley, plains, river ,ocean and seas. All these features make our earth a very beautiful place to live on.
Internal structure of the earth.
Just s an onion is made up of various layers the earth is also made up of three concentric layers . These layers are the crust, the mantle and the core.
The structure of the earth is similarly to that of an egg. The earth's crust is like the cell of an egg its mentle is like the egg white and the core is like the yolk.
Crust
The crust is the topmost soil layer. It is the coolest of the three layer. It is very thin. It thickness varies from around 5 km ( in the ocean floor ) to around 70 km ( the land where we live, called the continental crust ). The crust is made up of solid rock, soil and sand.
Mantle
The middle layer of the earth is called the mentle. It nice just beneath the crust.
It can be divided into two parts.
➢ The upper mantle
➢ The lower mantle
The upper mantle
The upper mantle is up 670 km below the Earth surface. It is made of both solid and melted rocks.
The lower mantle
The lower mantle is found between 670 km and 2890 km below the surface. Is it is made of solid rock . The rock is hot enough to melt , but is solid due to the pressure over it.
Core
This is inner most part of the earth. It lies below the metal and in the centre part of the earth.
The core is divided into two parts.
➢ The outer core
➢ The inner core.
The outer core
The outer core extends to a depth of around 5150km beneath the surface. It is made of iron and nickel and is very hot. The temperature ranges between 4,000°C and 5,000°C . This is so hot that the iron and nickel these are liquid.
The inner core
The inner core is a huge metal ball. It extend another 1,500km toward the centre of the earth. It is mainly mad of iron. But the metal stays solid because of the inner immense pressure surrounding it. The inner core is the hottest part of the earth. The temperature of the ball is about 6,000°C almost as hot as the surface of the sun.
