If our planet was an orange and we couldwould cut it in half, we would see several of its components. The earth's crust is located on the outer layer, which resembles the skin of a fruit. The soil on which we walk in the yard, the park, on the field, is the outer part of the shell, descending for 24-48 km inland. Breaking through the sand or dust in order to find out what the earth's crust is located on, you can eventually reach the rocks.
Most of the cortex beneath the continents consists oflayers of granite. In places like the Grand Canyon, where water partially damaged the shell, such places can be seen with the naked eye. Under the ocean floor, it extends only 5 km and consists mainly of another stone - basalt.
The Earth's crust accounts for 0.8% of the planet's total mass. The solid core is surrounded by a liquid shell, which consists mainly of iron in the liquid state. This two-layer core, in turn, is surrounded by a mantle of molten silicon and magnesium, as well as a thick layer of magma. The latter substance has a unique composition. Magma - a mixture of molten stone and gases, constantly residing under high pressure. Since the earth's crust is located on the mantle, sometimes the volcanic mass pours out during the eruption. In doing so, it penetrates into the splits and holes on the surface. Volcanoes, erupting, from time to time weaken the pressure of the magma.
Under the layer where the Earth's crust is located, liesa huge mantle, the thickness of 2880 km. Scientists do not know much about the structure of this layer of the planet. Its upper part consists mainly of a stone called peridotite. The Earth's crust is located on the mantle, beneath which is the core of the Earth. It is another 3200 km down to the center.
The oldest part of the earth's shell is located inWest Greenland, which appeared 4 billion years ago. It's 1 billion years after the hot clouds of cosmic gas and dust created the planet. Where is the earth's crust of the smallest age? Infants compared to the age of the Earth are the Canary Islands, located near the western African coast. They appeared subsequently underwater volcanic eruptions. For example, the island of La Palma has only 1 million years.
As for the lithosphere, it is known for sure that itbelongs to two layers - the earth's crust and the solid part of the mantle beneath it. In other words, the lithosphere is the solid shell of our planet, which lies above the asthenosphere.
It is interesting that the average thickness of the Earth's shellis 33 km, but on continents it varies from 25-45 km - on platforms and up to 45-75 km - in mountain systems. Depending on what the earth's crust is located on, the density of matter and its chemical composition varies. Such a difference is palpable at the border of the transition to the mantle.
It is characterized by its mineral compositionmainly low-melting silicates with the majority of aluminosilicates, and in terms of chemical composition, an increased concentration of silica, alkaline and rare metals with a reduced content of magnesium and elements of the iron group.
According to the peculiarities of the geological structure,geophysical properties and chemical compositions of the earth's crust are divided into 2 types - continental and oceanic. In addition, a transitional (or intermediate) type is also distinguished.
In the continental shell sedimentary,granite and basalt layers. Why is that? The names of the granite and basalt layers are conditional, taking into account not only the advantage of the corresponding rocks, but also geophysical properties. This is also related to the composition. The name of the basalt layer is also arbitrary. Because it contains many other magmatic rocks besides the main basalts, they are similar in geophysical properties.
The transition crust has both continental and oceanic properties. Depending on which features predominate in it, two subtypes are distinguished, such as sub-oceanic and sub-continental.
The earth's crust is located on sedimentary rocks. It also has features. Sedimentary layer consists of sedimentary rocks of marine and continental origin, has a predominant distribution on the continents and at the bottom of the oceans and seas. In places of access to the surface of the land, it is often completely absent. But within the large depressions reaches many kilometers, and in the Caspian depression - up to 25 km. Here is the largest thickness of sedimentary rocks on our planet. Their average density is 2.2 g / cm3, the temperature is less than 100 ° C.
The granite layer lies under the sedimentary layer andis distributed on all continents. In many places it can be observed directly in river valleys and beams. The density of rocks in this case is 2.4-2.6 g / cm3. The thickness of the layer within the platforms is an average of about 20 km, and under the mountain massifs - up to 40 km.
Basalt layer does not surface on the surface, and thoseBasaltic rocks that can be seen are effusions on the surface of lava as a result of ancient volcanic activity. They can be observed in the walls of rift valleys of mid-ocean ridges with the help of television cameras, and sampling is performed by drilling and automatic underwater vehicles. But this does not always happen that way. In the Red Sea, geologists selected the rocks with their own hands. Basalt layer lies under the granite layer, has a continuous distribution on the Earth. Its thickness on the continents is close to granite: mostly 20-25 km, and a maximum of 40 km. Under the ocean, it becomes much thinner and varies mainly from 4 to 10 km. The density of rocks is 2.8-3.3 g / cm3.
The earth's crust is located so that it is inconstant movement: the continents very slowly, but aggressively rotate on the liquid basis of the Earth. They connect with each other and diverge. The Earth looked completely different 200 million years ago. Then it was a huge single piece of land, surrounded by the sea. Later, separate blocks broke away from this ancient continent. 65 million years ago there were such parts of the Earth: the Eurasian continent, the united African-American continent, and also the part that formed today's Antarctica. The land area, where today India is located, was at that time an island.
The process of renewal of the Earth occurs constantly. Africa at a speed of several millimeters per year is approaching Europe, America is increasingly moving away from Africa. And in the place where India every year more and more tightly pressed to the Asian part of the land, the mountain ranges of the Himalayas rise. Because of this, the Himalayas are constantly growing, becoming taller. Tibet, located on this mountain range, during the last 2 million years, during the life of human life, grew 3 km up.
If the continents move from the previousspeed, then in the future the Earth will have a completely different form. After 50 million years, Alaska will connect with Siberia. The Mediterranean Sea will disappear, and as a consequence, Asia, Europe and Africa can form a single land area.