Ozone in the Stratosphere

This is a computer drawing of the two main chlorofluorocarbon (CFCs) molecules that release chlorine in the stratosphere, ultimately causing the destruction of ozone molecules.
Click on image for full size (294 Kb)
Courtesy of COMET program

About 90% of the ozone in the Earth's atmosphere lies in the region called the stratosphere which is found between 16 and 48 kilometers (10 and 30 miles) above the Earth's surface. Ozone forms a kind of layer in the stratosphere, where it is more concentrated than anywhere else, but even there it is relatively scarce. Its concentrations in the ozone layer are typically only 1 to 10 parts of ozone per 1 million parts of air.

Ozone and oxygen molecules in the stratosphere absorb ultraviolet light from the Sun, providing a shield that prevents this radiation from passing to the Earth's surface. While both oxygen and ozone together absorb 95 to 99.9% of the Sun's ultraviolet radiation, only ozone effectively absorbs the most energetic ultraviolet light, known as UV-C and UV-B, which causes biological damage. The protective role of the ozone layer in the upper atmosphere is so vital that scientists believe life on land probably would not have evolved - and could not exist today - without it.

The term "shield" as a description of ozone in the stratosphere is a bit misleading because the molecules do not form an impermeable sphere around the Earth. Ozone continuously breaks apart into its oxygen atoms and reforms as ozone molecules, so a particular ozone molecule doesn't last very long. The "shield" changes constantly, but the atmospheric chemical processes maintain a dynamic equilibrium that keeps the overall amount of ozone constant - that is, it would if humans did not contribute to the chemical processes. There is compelling scientific evidence that ozone is destroyed in the stratosphere and that some human-released chemicals such as CFC’s are speeding up the breakdown of ozone in the atmosphere.

While the stratospheric ozone issue is a serious one, in many ways it can be thought of as an environmental success story. Scientists detected the developing problem, and collected the evidence that convinced governments around the world to take regulatory action. Although the global elimination of ozone-depleting chemicals from the atmosphere will take decades yet, we have made a strong and positive beginning. For the first time in our species' history, we have tackled a global environmental issue on a global scale.


Introduction to Ozone Reading Activity

Ozone - An Overview

Ozone in the Stratosphere

This is a computer drawing of the two main chlorofluorocarbon (CFCs) molecules that release chlorine in the stratosphere, ultimately causing the destruction of ozone molecules.
Click on image for full size (294 Kb)
Courtesy of COMET program

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. Ozone forms a kind of layer in the stratosphere, where it is more concentrated than anywhere else.

Ozone and oxygen molecules in the stratosphere absorb ultraviolet light from the Sun, providing a shield that prevents this radiation from passing to the Earth's surface. While both oxygen and ozone together absorb 95 to 99.9% of the Sun's ultraviolet radiation, only ozone effectively absorbs the most energetic ultraviolet light, known as UV-C and UV-B. This ultraviolet light can cause biological damage like skin cancer, tissue damage to eyes and plant tissue damage. The protective role of the ozone layer in the upper atmosphere is so vital that scientists believe life on land probably would not have evolved - and could not exist today - without it.

The ozone layer would be quite good at its job of protecting Earth from too much ultraviolet radiation - that is, it would if humans did not contribute to the process. It's now known that ozone is destroyed in the stratosphere and that some human-released chemicals such as CFC’s are speeding up the breakdown of ozone, so that there are "holes" now in our protective shield.

While the stratospheric ozone issue is a serious one, in many ways it can be thought of as an environmental success story. Scientists detected the developing problem, and collected the evidence that convinced governments around the world to take action. Although the elimination of ozone-depleting chemicals from the atmosphere will take decades yet, we have made a strong and positive beginning. For the first time in our species' history, we have tackled a global environmental issue on a global scale.


Introduction to Ozone Reading Activity

Ozone - An Overview

Ozone in the Stratosphere

This is a computer drawing of the two main chlorofluorocarbon (CFCs) molecules that release chlorine in the stratosphere, ultimately causing the destruction of ozone molecules.
Click on image for full size (294 Kb)
Courtesy of COMET program

Most of the ozone that we know about is found in the the stratosphere, the second layer of the Earth's atmosphere. Ozone forms a kind of layer in the stratosphere. This layer shields us from the Sun's ultraviolet light. This ultraviolet light can cause damage to people like giving them skin cancer or causing tissue damage to their eyes. Ultraviolet light can also be bad for plants and animals.

The ozone layer would be very good at its job of protecting Earth from too much ultraviolet radiation - that is, it would if humans did not contribute to things! Human-released chemicals are speeding up the breakdown of ozone, so that there are "holes" now in our ozone protection shield.

Scientists know about this problem. They have told governments around the world that they need to stop making and releasing these harmful chemicals that break down ozone in the stratosphere. Countries have started doing this, and scientists are hoping that this will eventually heal the "holes" that were made in the ozone shield.


Introduction to Ozone Reading Activity

Ozone - An Overview


Page created June 11, 2004 by Jennifer Bergman.
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