As we saw in a previous post, the planet Earth It has many internal and external layers and is made up of four subsystems. The layers of the Earth they were in the subsystem of the geosphere. On the other hand, we had the biosphere, that area of the Earth where life develops. The hydrosphere was the part of the Earth where water exists. We only have the other subsystem of the planet, the atmosphere. What are the layers of the atmosphere? Lets go see it.
The atmosphere is the layer of gases that surrounds the Earth and that has various functions. Among these functions is the fact of housing the amount of oxygen necessary to live. Another vital function that the atmosphere has for living beings is to protect us from the sun's rays and external agents from space such as smaller meteorites or asteroids.
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Composition of the atmosphere
The atmosphere is made up of different gases in different concentrations. It is mostly composed of nitrogen (78%), But this nitrogen is neutral, that is, we breathe it but we do not metabolize it or use it for anything. What we do use to live is oxygen found at 21%. All living things on the planet, except anaerobic organisms, need oxygen to live. Lastly, the atmosphere has a very low concentration (1%) from other gases such as water vapor, argon, and carbon dioxide.
As we saw in the article on atmospheric pressure, the air is heavy, and therefore there is more air in the lower layers of the atmosphere because the air from above pushes the air below and is denser on the surface. It is because of that 75% of the total mass of the atmosphere it is located between the earth's surface and the first 11 kilometers in altitude. As we grow in altitude, the atmosphere becomes less dense and thinner, however, there are no lines that mark the different layers of the atmosphere, but more or less the composition and conditions change. Karman's line, about 100 km high, is considered the end of the Earth's atmosphere and the beginning of outer space.
What are the layers of the atmosphere?
As we have commented previously, as we ascend, we are finding the different layers that the atmosphere has. Each one with its composition, density and function. The atmosphere has five layers: The troposphere, stratosphere, mesosphere, thermosphere and exosphere.
The first layer of the atmosphere is the troposphere and is the closest to the earth's surface and therefore, it is in that layer that we live. It extends from sea level to about 10-15 km high. It is in the troposphere where life develops on the planet. Beyond the troposphere the conditions do not allow the development of life. The temperature and atmospheric pressure are decreasing in the troposphere as we increase the height at which we find ourselves.
Meteorological phenomena as we know them occur in the troposphere, since from there the clouds do not develop. These meteorological phenomena are formed by the uneven heating caused by the sun in the different regions of the planet. This situation causes the convection of currents and winds, that accompanied by changes in pressure and temperature, give rise to stormy cyclones. Airplanes fly inside the troposphere and as we have named before, outside the troposphere no clouds form, so there are no rains or storms.
In the highest part of the troposphere we find a boundary layer called tropopause. In this boundary layer, the temperature reaches very stable minimum values. That is why many scientists call this layer as "Thermal layer" Because from here, the water vapor in the troposphere cannot rise any further, as it is trapped when it changes from vapor to ice. If not for the tropopause, our planet could lose the water we have as it evaporates and migrate to outer space. You could say that the tropopause is an invisible barrier that keeps our conditions stable and allows the water to remain within reach.
Continuing with the layers of the atmosphere, we now find the stratosphere. It is found from the tropopause and extends from 10-15 km in height to 45-50 km. The temperature in the stratosphere is higher in the upper part than in the lower part since as it increases in height, it absorbs more solar rays and your temperature increases. That is to say, the behavior of the temperature in height is the opposite to that in the troposphere. It starts out stable but low and as the altitude increases, the temperature increases.
The absorption of light rays is due to the ozone layer which is between 30 and 40 km high. The ozone layer is nothing more than an area where the concentration of stratospheric ozone is much higher than in the rest of the atmosphere. Ozone is what protects us from the harmful rays of the sunBut if ozone occurs on the earth's surface, it is a strong atmospheric pollutant that causes skin, respiratory and cardiovascular diseases.
In the stratosphere there is hardly any movement in the vertical direction of the air, but the winds in the horizontal direction can reach frequently 200 km / h. The problem with this wind is that any substance that reaches the stratosphere is diffused throughout the entire planet. An example of this are CFCs. These gases composed of chlorine and fluorine destroy the ozone layer and spread throughout the planet due to strong winds from the stratosphere.
At the end of the stratosphere is the stratopause. It is an area of the atmosphere where high concentrations of ozone end and the temperature becomes very stable (above 0 degrees Celsius). The stratopause is the one that gives way to the mesosphere.
It is the layer of the atmosphere that extends from 50 km to more or less 80 km. The behavior of the temperature in the mesosphere is similar to that of the troposphere, since it descends in altitude. This layer of the atmosphere, despite being cold, is able to stop meteorites as they fall into the atmosphere where they burn, in this way they leave traces of fire in the night sky.
The mesosphere is the thinnest layer of the atmosphere, since only contains 0,1% of the total air mass and in it temperatures of up to -80 degrees can be reached. Important chemical reactions occur in this layer and due to the low density of the air, various turbulences are formed that help spacecraft when they return to Earth, since they begin to notice the structure of the background winds and not only the aerodynamic brake. of the ship.
At the end of the mesosphere is the mesopause. It is the boundary layer that separates the mesosphere and the thermosphere. It is about 85-90 km high and in it the temperature is stable and very low. Chemiluminescence and aeroluminescence reactions take place in this layer.
It is the broadest layer of the atmosphere. It extends from 80-90 km up to 640 km. At this point, there is hardly any air left and the particles that exist in this layer are ionized by ultraviolet radiation. This layer is also called ionosphere due to the collisions of the ions that take place in it. The ionosphere has great influence on the propagation of radio waves. A part of the energy radiated by a transmitter towards the ionosphere is absorbed by the ionized air and another is refracted, or deflected, back towards the surface of the Earth.
The temperature in the thermosphere is very high, reaching up to thousands of degrees Celsius. All the particles found in the thermosphere are highly charged with energy from the sun's rays. We also find that the gases are not evenly dispersed as is the case with the previous layers of the atmosphere.
In the thermosphere we find the magnetosphere. It is that region of the atmosphere in which the Earth's gravitational field protects us from the solar wind.
The last of the layers of the atmosphere is the exosphere. This is the layer furthest from the earth's surface and due to its height, it is the most indefinite and therefore not in itself considered a layer of the atmosphere. More or less it extends between 600-800 km in height up to 9.000-10.000 km. This layer of the atmosphere is what separates planet Earth from outer space and in it the atoms escape. It is composed mostly of hydrogen.
As you can see, different phenomena occur in the layers of the atmospheres and have different functions. From the rain, the winds and the pressures, through the ozone layer and the ultraviolet rays, each one of the layers of the atmosphere has its function that makes life on the planet as we know it.
The history of the atmosphere
La atmosphere that we know today it has not always been like this. Since the planet Earth was formed until today, millions of years have passed, and this has caused changes in the composition of the atmosphere.
The first Earth's atmosphere to exist arose from the largest and longest-lasting rain in history that formed the oceans. The composition of the atmosphere before life as we know it arose was made up mostly of methane. Back then, it does more than 2.300 billion years, the organisms that survived these conditions were organisms methanogens and anoxic, that is, they did not need oxygen to live. Today methanogens live in the sediments of lakes or the stomachs of cows where there is no oxygen. The planet Earth was still very young and the sun shone less, however, the concentration of methane in the atmosphere was about 600 times more than there is today with pollution. That translated into a greenhouse effect strong enough to be able to increase global temperatures, since methane retains a lot of heat.
Later, with the proliferation of cyanobacteria and algae, the planet filled with oxygen and changed the composition of the atmosphere until, little by little, it became what we have today. Thanks to plate tectonics, the reorganization of the continents contributed to the distribution of carbonate to all parts of the Earth. And that is why the atmosphere was transforming from a reducing atmosphere to an oxidizing one. The oxygen concentration was showing high and low peaks until it more or less remained at a constant concentration of 15%.