What are the principal layers of the atmosphere of Earth?

Earth is the lone planet in the Solar System that can support life. Thanks to its atmosphere and the array of gases it holds, we can breathe and remain safe from the harmful rays and radiation of the Sun. 

Earth’s atmosphere is roughly 480 kilometers or 300 miles thick. It is divided into five principal layers, namely the troposphere, the stratosphere, the mesosphere, the thermosphere, and the exosphere. The atmosphere dwindles every segment until it gradually thins out into interplanetary space.

Atmosphere of Earth

The troposphere is the first layer of the atmosphere and is the closest to the Earth’s surface. It stretches 7 to 20 kilometers or 4 to 12 miles above sea level. Moreover, it is also the densest layer consisting of three-quarters of the atmosphere’s mass. The air tends to be warmer from the ground and gets cooler moving up. Plus, almost all of the dust and water vapor is found in the troposphere, which is why clouds form in this layer. If you feel the breeze, see the clouds, or witness birds soaring, you’re in the troposphere.

The second layer is the stratosphere. It lies on top of the troposphere and extends 50 kilometers or 31 miles above sea level. The ozone layer or ozone shield lies in the stratosphere. It contains a high concentration of ozone that absorbs most of the Sun’s high-energy ultraviolet rays. In the process, it converts radiation into heat, making the stratosphere hotter as you move up the layer. The increasing temperatures imply that there are less turbulence and updrafts in this layer. With that, airplanes and jets fly in the stratosphere since there is less friction, allowing better gas mileage.

The third layer of the atmosphere is the mesosphere, which starts at the end of the stratosphere and stretches 85 kilometers or 53 miles high. The mesopause, the topmost part of the mesosphere, is the coldest portion of the planet’s atmosphere. Its temperature averages negative 90° Celsius or negative 130° Fahrenheit. With that, the mesosphere remains mysterious as it is harder to study. Aircraft don’t reach the mesosphere while satellites orbits higher than the layer. Scientists, however, know that meteors dissolve or burn up in the mesosphere. Some fragments still remain in the mesosphere, which is why it has a relatively high volume of metal atoms.

The fourth layer of the atmosphere is the thermosphere that starts from 90 kilometers to 56 miles above sea level and stretches up to 500 to 1,000 kilometers or 310 to 620 miles. While this layer is still regarded as part of the planet’s atmosphere, its air density is incredibly low, allowing people to think of it as outer space. Most say that space starts between the mesopause and thermosphere. Truth to be told, space shuttles and space stations orbit in the mesosphere. Plus, this is also where aurora australis and aurora borealis light occur. Atoms and molecules present in the thermosphere run into charged particles from space, causing them to release high energy in forms of light or the colorful auroras.

The last region and the uppermost layer of the Earth’s atmosphere is the exosphere. It contains extremely thin air, making it resemble space even greater than the thermosphere. The air in the exosphere always slowly leaks into outer space. While there is no exact line that defines the end of the exosphere, experts place it around 100,000 kilometers or 62,000 miles to 190,000 kilometers or 120,000 miles above sea level. It still contains gases like hydrogen and helium but very scattered, minimizing the likelihood of atom collisions.

More Readings

Atmosphere (Wikipedia)

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