User:Samia fayal/Outline of Earth sciences

The globe is mainly composed of four shells: the lithosphere, the hydrosphere, the atmosphere, and the biosphere. [1]

Atmosphere
It is that envelope that surrounds the earth from all sides and starts from the surface of the earth, where the sea surface represents the lower boundary of the atmosphere and rises to infinity in the atmosphere

The atmosphere consists of two main components, which represent about 99% of the air, where nitrogen is 78% of the air and oxygen is 21% of the air and the rest are many different gases, the most important of which is carbon dioxide, and the density of gases in this atmosphere increases as we approach the surface of the earth due to the increase in pressure, And it decreases as we move away from the surface of the earth, so that in the upper atmosphere we find very few and light gases such as hydrogen gas and helium.

Some scholars divided this cover into four sections, which are as follows:

The lowest atmosphere, which is in contact with the surface of the earth, to a height of approximately 60 km.

The higher atmosphere, which follows the lower atmosphere and reaches a height of about 90 km, contains the ozone layer that protects and reduces the ultraviolet rays from the sun.

The ionic atmosphere, which reaches a height of about 500 km, contains ionized gases, and the air is thin and loose.

The outer atmosphere, which extends to infinity in the universe, contains light gases such as helium and hydrogen that are part of the mixture of planetary gases.

Lithosphere.
It is the most important envelope of the Earth in geology, and it represents those different and disparate rocks and minerals that make up the surface (crust) of the earth on which we live.

The lithosphere is affected by all the other wrappings. As it contributes very greatly to the formation of its features. And determine the forms and types of its rocks and minerals.

The biosphere is the space in which life exists and extends from the deepest depth in which life is found in the seas to the highest elevation at which life is found in the mountains. Its thickness is approximately 14 km.

Hydrosphere
Water covers about 70% of the surface of the earth, and the seas and oceans are the most important forms of water on the surface of the earth, as they represent about 97% of the water on earth. There are other forms of water on the ground such as clouds, rivers, ice and groundwater, which also have an active role in geological processes.

The water on the surface of the earth is constantly replenished through the water cycle in nature

Biosphere
It is that domain in which the various forms of life are represented on the surface of the earth, as it contains all the living organisms that exist and influence in one way or another on the surface of the earth and are involved in various geological processes such as sculpture and sedimentation. The biosphere also includes those organisms that were found on the surface of the earth during different geological ages and then disappeared and became extinct.

The stages of formation of the Earth's shells
At the beginning of the formation of the Earth, the rotation of our planet around itself and its continued gradual warmth played a major role in rearranging its components according to their density.