Our earth

We are living on the land. A great nature is on the earth. That nature is very beautiful.

What is the earth made of?

The earth is a big ball, or sphere, made mostly of rock. The inside is molten rock, but the outside cover is hard rock. Then inside is molten rock, but the out side cover is herd rock.

The outside of the earth is a crust of rock, called lithosphere, about 10 to 30 miles thick. The high parts of this crust are the continents, and the low parts of it hold the waters of the oceans, sea and lakes. All the water on the surface is called the hydrosphere.

The crust of the earth has two layers.

1) The upper layer- made of granite

2) The thicker layer-made of basalt.

Between the central ball and rocky crust is a sell abut 2,000 miles thick called mantle.

In drilling wells and mines, it has been found that the deeper the hole is made, the higher the temperature becomes. At two miles below the surface of earth, the temperature is high enough to boil water.

At the core, the temperature is believed to be as high as 10,000 foreign heat degrees.

The fast move of earth

The earth has two motions.-it spins on its axis and it moves in an orbit around the sun.

The period of rotation through 360 degrees (it is, one complete turn of the earth) takes 23 hours, 56 minutes and 4.091 seconds.

It was believed that the speed of the rotation never changed, but is has been found that there are tiny variations. Because of the friction of ocean tides and changes in the earth’s crust, our day may be getting longer at the rate of about one thousand of a second per century.

A planet moves faster when it is closer to the sun and since the sun does not stay the same at all times, the orbital speed is constantly changing.