If our planet was an orange and we could 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, park, on the field is the outer part of the shell, which falls 24-48 km inland. Breaking through sand or dust in order to find out what the earth’s crust is located on, in the end you can get to the stones.
Earth structure
Most of the crust beneath the continents consists of layers 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 total mass of the planet. The solid core is surrounded by a liquid shell, which consists mainly of iron in a 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 is a mixture of molten stone and gases, constantly under high pressure. Since the earth’s crust is located on the mantle, sometimes a volcanic mass spills out during an eruption. In this case, it penetrates into the splits and holes on the surface. Volcanoes erupting from time to time weaken the pressure of magma.
Under the layer where the earth’s crust is located, lies a huge mantle, 2880 km thick. 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, under which is the core of the Earth. It is located another 3200 km down to the very center.
The oldest and youngest parts of the earth's crust
The oldest part of the earth’s shell is located in West Greenland, which appeared 4 billion years ago. This is 1 billion years after the hot clouds of cosmic gas and dust created the planet. Where is the smallest age crust located? Infants compared to the age of the Earth are the Canary Islands, located near the west African coast. They appeared subsequently underwater volcanic eruptions. For example, the island of La Palma is only 1 million years old.
Lithosphere and Earth's crust
As for the lithosphere, it is known for sure that it belongs to two layers - the earth's crust and the solid part of the mantle located below 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 shell is 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 the substance and its chemical composition changes. Such a difference is noticeable on the border of the transition to the mantle.
In terms of its mineral composition, it is characterized mainly by low-melting silicates with most aluminosilicates, and by its chemical composition - by an increased concentration of silica, alkali and rare metals with a low content of magnesium and elements of the iron group.
Types of Earth Shell
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 are sedimentary, granite and basalt layers. Why is that? The names of the granite and basalt layers are arbitrary, taking into account not only the advantage of the corresponding rocks, but also the geophysical properties. This is due to the composition. The name of the basalt layer is also arbitrary. Because it contains, in addition to basic basalts, many other igneous rocks, but they are similar in geophysical properties.
The transitional crust has the properties of both continental and oceanic. Depending on which features prevail in it, two subtypes are distinguished, such as suboceanic and subcontinental.
Sediment layer
The crust is located on sedimentary rocks. It also has features. The 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 land surface, it is often completely absent. But within the limits of large depressions it 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 / cm 3 , the temperature is less than 100 ° C.
Granite layer
The granite layer lies under the sedimentary layer and is distributed on all continents. In many places it can be observed directly in the river valleys and gullies. The density of the rocks in this case is 2.4-2.6 g / cm 3 . The layer thickness within the platforms is on average about 20 km, and under mountain ranges - up to 40 km.
Basalt layer
The basalt layer does not come to the surface, and those basalt rocks that can be seen are outpourings on the surface of the lava as a result of ancient volcanic activity. They can be observed in the walls of the rift valleys of the mid-ocean ridges using cameras, and sampling is performed by drilling and automatic underwater vehicles. But this is not always the case. In the Red Sea, geologists selected rocks with their own hands. The basalt layer lies under the granite layer, has a continuous distribution on the Earth. Its thickness on the continents is close to granite: mainly 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 the rocks is 2.8-3.3 g / cm 3 .
Inconsistency of the Earth's crust
The Earth’s crust is located in such a way that it is in constant motion: the continents are very slowly but persistently 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 boulders split from this ancient continent . 65 million years ago, such parts of the Earth existed: the Eurasian continent, the united African American continent, and also the part that formed today's Antarctica. The land area where India is located today was an island in those days.
The process of updating the Earth is ongoing. Africa with a speed of several millimeters per year is approaching Europe, America is increasingly moving away from Africa. And in the place where India is more and more pressed against the Asian part of the land every year, the mountain ranges of the Himalayas rise. Because of this, the Himalayas are constantly growing, becoming higher. Tibet, located on this mountain range, over the past 2 million years, during the existence of human life, has grown 3 km up.
If the continents move at a previous speed, then in the future the Earth will have a completely different look. After 50 million years, Alaska will unite with Siberia. The Mediterranean Sea will disappear, and as a result, Asia, Europe and Africa can form a single piece of land.