This graph shows how the amount of ozone in the air is greater in the stratosphere. The most ozone is found at an altitude between 20 and 25 km (12 and 16 miles).
Click on image for full size
Image courtesy of NOAA, modified by Windows to the Universe staff.
The ozone layer is a range of altitudes in Earth's stratosphere which has a higher concentration of ozone molecules. Ozone is an unusual type of oxygen molecule. It is created when high-energy ultraviolet light from the Sun strikes a normal oxygen molecule.
The ozone layer extends from roughly 15 to 35 km (9 to 22 miles) above sea level. The peak of ozone concentration is between 20 and 25 km (12 and 16 miles). Concentrations typically range between 2 and 8 parts per million, though they can rise as high as 15 parts per million. About 90% of the ozone in our atmosphere is contained in the stratosphere. The ozone layer isn't actually a separate layer of Earth's atmosphere; it is a region within the stratosphere.
Ozone in the stratosphere protects us from ultraviolet radiation in sunlight. The ozone layer is sort of like sunscreen for planet Earth. It absorbs most of the incoming UV "light" before it reaches the ground. The ozone layer stops almost all of the incoming UV-C, about 90% of the UV-B, and roughly half of the UV-A radiation. The ozone molecules which absorb UV radiation later re-radiate the energy as heat, warming the stratosphere.
Various chemicals that humans release into the atmosphere can destroy ozone in the stratosphere. That is a problem since it allows more UV radiation to make it to the surface. In the 1980s, scientists noticed that the ozone layer was thinning. They also noticed huge holes in the ozone layer, especially over Antarctica. They convinced people and governments around the world to reduce emissions of ozone-destroying chemicals. They hope the ozone layer will heal itself over time.
Shop Windows to the Universe Science Store!
The Fall 2009 issue of The Earth Scientist
, which includes articles on student research into building design for earthquakes and a classroom lab on the composition of the Earth’s ancient atmosphere, is available in our online store
You might also be interested in:
Ozone is a special kind of oxygen molecule. Normal oxygen molecules (O2), the kind we need to breathe, have two oxygen atoms. Ozone molecules (O3) have three oxygen atoms. Ozone forms when a photon of...more
Oxygen (O2) is a kind of gas. A lot of the air you breathe is oxygen. That's a good thing, since we need oxygen to stay alive! About 4/5ths of the air in Earth's atmosphere is nitrogen (N2). Almost all...more
About 90% of the ozone in the Earth's atmosphere is found in the region called the stratosphere. This is the atmospheric layer between 16 and 48 kilometers (10 and 30 miles) above the Earth's surface....more
What do smog, acid rain, carbon monoxide, fossil fuel exhausts, and tropospheric ozone have in common? They are all examples of air pollution. Air pollution is not new. As far back as the 13 th century,...more
Rainbows appear in the sky when there is bright sunlight and rain. Sunlight is known as visible or white light and is actually a mixture of colors. Rainbows result from the refraction and reflection of...more
The Earth travels around the sun one full time per year. During this year, the seasons change depending on the amount of sunlight reaching the surface and the Earth's tilt as it revolves around the sun....more
Scientists sometimes travel in specially outfitted airplanes in order to gather data about atmospheric conditions. These research aircraft have special inlet ports that bring air from the outside into...more