This is a conventional division. One layer does not finish abruptly where another starts, but there are progressive steps. We start from the troposphere, which reaches the cruising altitude of a 747: 10 thousand meters. Below this is the Earth’s surface, including the highest mountain on the planet, Everest, which reaches 8848 meters. Already at this altitude the presence of oxygen is lower: that is why after eight thousand meters it is said that you enter the "death zone".
Over 10 km above our heads is the stratosphere. It reaches 50 km of altitude and consists of rarefied gases that are arranged in layers, according to their density. One of the characteristics of the stratosphere is the presence of strong horizontal winds called "jet streams". Between 20 and 30 km above the earth’s surface, among other things, we find the famous ozone. It is a very important gas for life on Earth, because it absorbs a large part of ultraviolet and cosmic rays, which are dangerous for living things.
Over 50 km high there is the mesosphere, made up of increasingly rarefied gases. Here the temperature is very low and can go up to a hundred degrees below zero. Most meteors disintegrate there. Higher up, we find the thermosphere, which reaches 500 km above sea level. Here the temperature rises, reaching up to 1500 ³ C: the reason is the absorption of ultraviolet rays. In this layer arise the polar auroras, these spectacular phenomena which in certain periods of the year can be observed at the poles of the Earth.
The exosphere, the outermost part of Earth’s atmosphere. Consider that it extends over 500 km and here the temperature reaches up to 2700 > C. The gases that compose it are extremely rarefied. This layer gradually becomes less dense and visible, until it dissolves into the cosmos.
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