The Earth’s Atmosphere

The Earth’s atmosphere is divided into four layers based on temperature. “The Troposphere is the bottom layer or the one closest to the Earth’s surface and is about 5 to 9 miles (8 to 14 km) being thicker around the equator and thinner near the poles. This is where our weather occurs, this layer is in constant movement. It is the densest layer containing about 3/4 of the mass of the entire atmosphere,” according to NASA Science Space Place. As you go higher in the Troposphere the temperature decreases. The border between the Troposphere and the next layer is the Tropopause.The next layer is the Stratosphere and this is where the ozone layer is. Ozone or O3 absorbs ultraviolet radiation from the sun; protection the surface of the Earth from these harmful rays. Because of this, the Stratosphere gets warmer above the Ozone layer. This layer reaches from approximately 7 miles to 30 mile (10 km to 48km) above the Earth’s surface. Then there is the Stratopause, the border between the Stratosphere and the next layer, the Mesosphere. The mesosphere rises from about 30 miles to 50 miles (48km to 80km) above the surface of the Earth and it gets colder as you go higher. At the start of the mesosphere the atmospheric pressure is about one-thousandth of the air pressure as sea level, but by the time you reach the mesopause (the top of the Mesosphere) the atmospheric pressure is only about one-millionth of that at sea level. Last we reach the Thermosphere layer that goes from about 50 miles to about 90 miles (80km to 140km). The temperature begins to increase again due to the absorption of very shortwave, and high-energy solar radiation by atoms of oxygen and nitrogen. There is also the Ionosphere that is part of the Thermosphere but rises up even higher to about 250 miles (400km) and this is where the aurora borealis (northern lights) and the aurora australis (southern lights) happen. It is an electrically charged area where molecules of nitrogen (N2 ) and atoms of oxygen are ionized by absorbing high-energy shortwave solar energy. This causes them to lose one or more electrons. “These reactions are what cause the light and colour of the northern and southern lights. The green light is associated with oxygen molecules and red is produced at higher attitudes, while blues and purples are associated with nitrogen molecules.” from the Northern Lights Centre website.

The composition of the atmosphere is approximately 78% Nitrogen, 21 % Oxygen, and 1% made up of Carbon dioxide, Argon, Neon, Helium, Methane, Krypton, Hydrogen. There are also variable gases and particles such as, water vapour, ozone (which is a pollutant at ground level), aerosols of dust, smoke, soot, pollens, and microorganisms, and pollutants, etc. Aerosols are tiny particles that can be solid or liquid.

Reference: The Atmosphere – An Introduction to Meteorology 12 Ed. by Lutgens & Tarbuck

For the most part, we cannot see what is in the air unless the pollution or smog is really bad, but just because you cannot see it doesn’t mean it can’t harm you. Humans are continually releasing toxic chemicals into the air, believing they will just dissipate. The Earth’s ecoservice systems cannot keep up with the constant bombardment of pollutants that us humans are releasing into the environment.

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