What does the earth's crust consist of? Elements of the Earth's crust

The Earth’s crust is the solid surface layer of our planet. It was formed billions of years ago and is constantly changing its appearance under the influence of external and internal forces. Part of it is hidden under water, the other forms land. The earth's crust is composed of various chemicals. Let's find out which ones.

Planet surface

Hundreds of millions of years after the emergence of the Earth, its outer layer of boiling molten rocks began to cool and formed the earth's crust. From year to year, the surface has changed. Cracks, mountains, volcanoes appeared on it. The wind smoothed them, so that after a while they appeared again, but in other places.

Due to external and internal processes, the outer solid layer of the planet is heterogeneous. From the point of view of structure, we can distinguish the following elements of the earth's crust:

• geosynclines or folded areas;
• platforms;
• edge faults and deflections.

Platforms are extensive inactive sections. Their upper layer (to a depth of 3-4 km) is covered by sedimentary rocks, which occur in horizontal layers. The lower level (foundation) is badly crushed. It is composed of metamorphic rocks and may contain magmatic inclusions.

Geosynclines are tectonically active sites where mountain building processes occur. They arise at the junction of the ocean floor and the continental platform, or in the deflection of the ocean floor between the continents.

If mountains form close to the platform boundary, edge faults and sagging can occur. They reach up to 17 kilometers in depth and stretch along a rock formation. Over time, sedimentary rocks accumulate here and mineral deposits are formed (oil, rock and potassium salts, etc.).

Composition of the bark

The mass of the crust is 2.8 · 1019 tons. This is only 0.473% of the mass of the entire planet. The content of substances in it is not as diverse as in the mantle. It is formed by basalts, granites and sedimentary rocks.

99.8% of the earth's crust consists of eighteen elements. The rest accounts for only 0.2%. The most common are oxygen and silicon, which make up the bulk of the mass. In addition to them, the bark is rich in aluminum, iron, potassium, calcium, sodium, carbon, hydrogen, phosphorus, chlorine, nitrogen, fluorine, etc. The content of these substances can be seen in the table:

Astatine is considered to be the rarest element - an extremely unstable and poisonous substance. Tellurium, indium, and thallium are also rare. Often they are scattered and do not contain large clusters in one place.

Continental crust

The continental or continental crust is what we usually call land. She is quite old and covers about 40% of the entire planet. Many of its sites reach the age of 2 to 4.4 billion years.

The continental crust consists of three layers. An intermittent sedimentary cover covers it from above. The rocks in it lie in layers or layers, as they are formed as a result of compression and compaction of precipitation of salts or residues of microorganisms.

The lower and more ancient layer is represented by granites and gneisses. They are not always hidden under sedimentary rocks. In some places they come to the surface in the form of crystalline shields.

The lowest layer consists of metamorphic rocks like basalts and granulites. The basalt layer can reach 20-35 kilometers.

Oceanic crust

Part of the earth's crust, hidden under the waters of the oceans, is called oceanic. It is thinner and younger than continental. By age, the crust does not reach even two hundred million years, and its thickness is about 7 kilometers.

The continental crust consists of sedimentary rocks from deep-sea residues. Below is a basalt layer 5-6 kilometers thick. Under it begins the mantle, represented here mainly by peridotites and dunites.

Every hundred million years, the crust is renewed. It is absorbed in subduction zones and forms again in the region of the mid-ocean ridges, with the help of outgoing minerals.