layers+of+the+earth

the layers of the earth are...




 * The crust covers the mantle and is the earth's hard outer shell, the surface on which we are living. Compared to the other layers the crust is much thinner. It floats upon the softer, denser [|mantle]. The crust is made up of solid material but this material is not the same everywhere. There is an Oceanic crust and a Continental crust. The first one is about 4-7 miles (6-11 km) thick and mainly consists of heavy rocks, like basalt. The Continental crust is thicker than the Oceanic crust, about 19 miles(30 km) thick. It is mainly made up of light material like granite.

The layer above the core is the mantle. It begins about 6 miles(10 km) below the oceanic crust and about 19 miles (30 km) below the continental crust (see The Crust). The function of the mantle is to separate the inner mantle and the outer mantle. It is about 1,800 miles(2,900 km) thick and makes up nearly 80 percent of the Earth's total volume. Science deals with the structure of the mantle in two different ways. One way is based on its chemical construction (the material), the other on the way layers stream or move.

The inner part of the earth is the core. This part of the earth is about 1,800 miles (2,900 km) below the earth's surface. The core is a dense ball of the elements iron and nickel. It is divided into two layers, the inner core and the outer core. The inner core - the center of earth - is solid and about 780 miles (1,250 km ) thick. The outer core is so hot that the metal is always molten, but the inner core pressures are so great that it cannot melt, even though temperatures there reach 6700ºF (3700ºC). The outer core is about 1,370 miles (2,200 km) thick. Because the earth rotates, the outer core spins around the inner core and that causes the earth's magnetism. || **Plate Tectonics** ** The [|earth's crust] consists of a number of moving pieces or plates, that are always colliding or pulling apart. The Lithosphere consists of nine large plates and twelve smaller ones. The continents are imbedded in continental plates; the oceanic plates make up much of the sea floor. The study of Tectonic plates - called plate tectonics - helps to explain continental drift, the spreading of the sea floor, [|volcanic eruptions] and how mountains are formed. The force that causes the movement of the tectonic plates may be the slow churning of the[|mantle] beneath them. Mantle rock is constantly moved upwards to the surface by the high temperatures below and then sinks by cooling. This cycle takes millions of years. ** ||

Divergent boundary : Occur where plate move parts and It The Ocean, Where the Ocean floor is spreading apart Rift valley.