Even today, when the invented many technical equipment, vehicles, still remain inaccessible and mysterious worlds.One of them are the bowels of the earth.The deepest well in the world drilled in the Kola peninsula, it reaches a depth of 12 km, which is only 1/500 of the radius of the planet.All that scientists know about the bowels of the earth, they learn by studying the seismic method.During concussions occur within the planet's vibrations that are carried by different speeds.It is known that the speed of propagation depends on the density and composition of substances.Based on the speed data assistants already may interpret information that has passed through a layer of oscillation.
It was thus found that the planet is covered with several shells.This is the crust, mantle, and then the next - the kernel.
Last - the most dense and heavy.It is believed that the core is composed of iron.
Mantle of the three membranes has the largest volume and weight.It consists of a solid, but not such dense as in the core.
And finally, the earth's crust.This outer shell of the planet is much thinner than previous.Its weight does not exceed even 1% of the weight of the entire planet.On the surface of the lives of mankind, it is extracted from minerals.In many places, the crust is penetrated by wells and mines.Their presence allowed to collect rock samples, which helped to define the structure of the shell of the planet.
A member of the crust of rock, which, in turn, are formed from minerals.They continue now be formed in all layers of the shell, even at its surface.In the conditions in which the rocks were formed, they are divided into:
1. Metamorphic.They are formed deep in the earth as a result of extreme heat and contraction of some rocks and their transformation into other breeds.For example, in the marble transforms ordinary limestone.
2. Sedimentary.They are formed by the gradual accumulation at the surface of various minerals.Since this process is slow, sedimentary rocks often consist of several layers.
3. Magmatic.They form the substance of the mantle, raised in the upper layers, and there frozen.The most famous of these rocks - granite.Magma may in molten form and to rise to the surface.Then it stand out from the water vapor and gases, and it turns into lava.Izlivshis, it freezes instantly.Thus, in the eruption formed igneous rocks.These include, for example, basalt.
earth's crust beneath the oceans and continents arranged differently.The main differences are the composition of its layers and thick.On this basis, separately consider the following types of the earth's crust:
- Continental;
- oceanic.
Experts suggest that mainland kind appeared much later under the influence of seismic processes occurring in the planet's interior.The minimum thickness of the continental (or continental), the Earth's crust - 35 km, and under the mountains and other elevations, it is up to 75 km.Form its three layers.Top - a sedimentary rock.Its thickness - from 10 km to 15 km.Then there is a 5-15-kilometer layer of granite.And the last - basalt.Its thickness - 10-35 km.It consists mainly of basalt, as well as species that are close to it on the physical properties.
chemical composition of the earth's crust can be determined only by its top layer having a depth less than 20 km.Almost half of it is occupied by the oxygen, 26% - silicon, about 8% - aluminum, 4.2% - iron, 3.2% - calcium at 2.3% - magnesium, potassium, and 2.2% - sodium.On the other chemical elements is not more than one tenth of 1%.
Now scientists undertook a close study of the oceanic crust and continental.They were founded upon the hypothesis of continents moving, put forward more than a century ago, Alfred Wegener, and formed his theory of the structure of the outer shell of the planet.
