What are the main properties of the atmosphere. History of formation and composition of the Earth's shell

The atmosphere is the outer shell of celestial bodies. On different planets it differs in composition, chemical and physical properties. What are the main properties of the Earth's atmosphere? What does it consist of? How and when did it arise? We will learn more about this.

Atmosphere formation

The atmosphere is a mixture of gases that envelop the planet from the outside and are held back by its gravitational forces. At the time of formation, our planet did not yet have a gas envelope. It was formed a little later and had time to change many times. It is not known to the end what the main properties of the atmosphere were then.

Scientists suggest that the very first atmosphere was picked up from the solar nebula and consisted of helium and hydrogen. The high temperatures of the planet and the effect of the solar wind quickly destroyed this shell.

The next atmosphere was formed due to volcanoes, which released gases from the Earth's mantle. It was thin and consisted of greenhouse gases (methane, carbon dioxide, ammonia), water vapor and acids.

Two billion years ago, the state of the atmosphere began to transform into the present. Participation in this took external processes (weathering, activity of the Sun) on the planet and the first bacteria and algae, due to the release of oxygen.

Composition and properties of the atmosphere

The gas shell of our planet does not have a clear edge. Its outer contour is blurred and gradually passes into outer space, merging with it into a homogeneous mass. The inner edge of the shell touches the Earth's crust and the Earth's hydrosphere.

What the basic properties of the atmosphere are, is largely determined by its composition. Most of it is represented by gases. The major part is accounted for by nitrogen (75.5%) and oxygen (23.1%). In addition, atmospheric air consists of argon, carbon dioxide, hydrogen, methane, helium, xenon, etc.

The concentration of substances practically does not change. Irregular values are typical for water and carbon dioxide. The content of carbon dioxide is determined by the amount of vegetation. Water is contained in the form of water vapor. Its number varies depending on geographical latitudes and amounts to 2.5%. In the atmosphere, combustion products, sea salt, impurities of dust, ice in the form of small crystals are also present.

Physical properties of the atmosphere

The main properties of the atmosphere are pressure, humidity, temperature and density. In each of the layers of the atmosphere their values differ. The air of the Earth's shell is a set of molecules of various substances. Forces of attraction keep them within the planet, pulling closer to its surface.

There are more molecules at the bottom, so there is more density and pressure there. With the height they decrease, but in outer space they become practically invisible. In the lower layers of the atmosphere, the pressure decreases by 1 mm Hg. Art. Every 10 meters.

Unlike the surface of the planet, the atmosphere does not heat up by the Sun. Therefore, the closer to the Earth, the higher the temperature. For every hundred meters it decreases by about 0.6 degrees. In the upper part of the troposphere it reaches -56 degrees.

Air parameters are strongly affected by the water content in it, that is, humidity. The total mass of the planet's air is (5.1-5.3) · 10 ¹⁸ kg, where the share of water vapor is 1.27 · 10 ¹⁶ kg. Since the properties of the atmosphere at different sites are different, standard values are derived, which are taken as "normal conditions" on the surface of the Earth:

The structure of the gas envelope of the Earth

The nature of the gas shell varies with height. Depending on what are the main properties of the atmosphere, it is divided into several layers:

• troposphere;
• stratosphere;
• mesosphere;
• thermosphere;
• exosphere.

The main parameter for differentiation is the temperature. Between the layers, boundary areas are identified, called pauses, in which a constant temperature is fixed.

The troposphere is the lowest layer. Its border runs at an altitude of 8 to 18 kilometers, depending on the latitude. Above all, it is on the line of the equator. Approximately 80% of the air mass of the atmosphere falls precisely on the troposphere.

The outer layer of the atmosphere is represented by an exosphere. Its lower limit and thickness depend on the activity of the Sun. On Earth, the exosphere starts at an altitude of 500 to 1,000 kilometers and reaches up to one hundred thousand kilometers. At the bottom, it is saturated with oxygen and nitrogen, at the top with hydrogen and other light gases.

The role of the atmosphere

The atmosphere is the air we breathe. Without him, a person will not live for five minutes. It saturates all cells of plants and animals, promoting the exchange of energy between the body and the environment.

The atmosphere is the filter of the planet. Passing through it, the solar radiation dissipates. This reduces its intensity and harm, which it can cause in a concentrated form. The shell plays the role of the shield of the Earth, in the upper layers of which many meteorites and comets burn, not reaching the surface of the planet.

The temperature, density, humidity and pressure of the atmosphere form the climate and weather conditions. The atmosphere participates in the distribution of heat on the planet. Without it, the temperature would fluctuate within two hundred degrees.

The Earth's shell participates in the circulation of substances, is the habitat of a part of living beings, facilitates the transmission of sounds. Her absence would make life impossible on the planet.