The Earth's crust is the hard 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 part forms land. The earth's crust is made up of various chemicals. Let's find out which ones.
The surface of the planet
Hundreds of millions of years after the formation of the Earth, its outer layer of boiling molten rocks began to cool and formed the earth's crust. The surface changed from year to year. Cracks, mountains, volcanoes appeared on it. The wind smoothed them out so that after a while they reappeared, but in other places.
Due to external and internal processes, the outer solid layer of the planet is not uniform. From the point of view of structure, the following elements of the earth's crust can be distinguished:
- geosynclines or folded areas;
- platforms;
- marginal faults and troughs.
Platforms are vast, sedentary areas. Their upper layer (up to a depth of 3-4 km) is covered with sedimentary rocks,which lie in horizontal layers. The lower level (foundation) is strongly crumpled. It is composed of metamorphic rocks and may contain igneous inclusions.
Geosynclines are tectonically active areas where mountain building processes take place. They occur at the junction of the ocean floor and the continental platform, or in the trough of the ocean floor between the continents.
If mountains form close to the edge of the platform, edge faults and troughs may occur. They reach up to 17 kilometers in depth and stretch along the mountain formation. Over time, sedimentary rocks accumulate here and mineral deposits (oil, rock and potassium s alts, etc.) are formed.
Composition of bark
The mass of the bark 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 bas alts, granites and sedimentary rocks.
At 99.8% of the earth's crust consists of eighteen elements. The rest account 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:
| Item name | symbol | % mass |
| Oxygen | O | 49, 13 |
| Silicon | Si | 26, 0 |
| Aluminum | Al | 7, 45 |
| Iron | Fe | 4, 2 |
| Calcium | Ca | 3, 25 |
| Sodium | Na | 2, 4 |
| Potassium | K | 2, 35 |
| Magnesium | Mg | 2, 35 |
| Hydrogen | H | 1 |
| Titanium | Ti | 0, 61 |
| Carbon | C | 0, 35 |
| Chlorine | Cl | 0, 2 |
| Phosphorus | P | 0, 125 |
| Sulfur | S | 0, 1 |
| Manganese | Mn | 0, 1 |
| Fluorine | F | 0, 08 |
| Barium | Ba | 0, 05 |
| Nitrogen | N | 0, 04 |
Astatine is considered the rarest element - extremely unstable andpoisonous substance. Tellurium, indium, and thallium are also rare. Often they are scattered and do not contain large clusters in one place.
Continental crust
Mainland or continental crust is what we commonly refer to as dry land. It is quite old and covers about 40% of the entire planet. Many parts of it are between 2 and 4.4 billion years old.
The continental crust consists of three layers. From above it is covered with a discontinuous sedimentary cover. The rocks in it lie in layers or layers, as they are formed as a result of pressing and compaction of s alt sediments or microorganism residues.
The lower and older 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 is composed of metamorphic rocks like bas alts and granulites. The bas alt 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. The age of the crust does not even reach two hundred million years, and its thickness is approximately 7 kilometers.
The continental crust is composed of sedimentary rocks from deep sea remnants. Below is a bas alt layer 5-6 kilometers thick. Below 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 re-formed at mid-ocean ridges with the help of outward minerals.
