Ozone Above Us: The Shield That Filters UV
Sunlight travels about 93 million miles to reach Earth. It warms the ground, helps plants grow, and brightens the sky. But sunlight also carries ultraviolet radiation, or UV, which can damage living things. High above us, a thin concentration of a gas called ozone absorbs much of the most harmful UV before it reaches the surface.
This protective region is known as the ozone layer. It is not a solid shell or a separate sheet wrapped around the planet. Instead, ozone molecules are scattered among other gases in the stratosphere, a part of the atmosphere that begins roughly 6 to 10 miles above Earth’s surface. Most atmospheric ozone is found there, with the greatest concentrations higher still.
A molecule with two sides
An ozone molecule contains three oxygen atoms. The oxygen gas people breathe usually has molecules made of two oxygen atoms. In the stratosphere, energetic UV radiation can split ordinary oxygen molecules apart. Free oxygen atoms can then join other oxygen molecules, forming ozone.
Ozone also absorbs UV radiation and breaks apart. It can form again when free oxygen atoms meet oxygen molecules. These processes happen continually, with ozone being made and destroyed in the stratosphere.
- radiation:
- Energy that travels through space or matter.
- concentration:
- The amount of a substance in a particular area or mixture.
- atmosphere:
- The layer of gases surrounding Earth.
- molecules:
- Groups of atoms joined together.
- pollutant:
- A substance that makes the environment harmful or dirty.
- stable:
- Not likely to change or react easily.
- ecosystems:
- Communities of living things and their surroundings.
- emissions:
- Substances released into the air.
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Preview questions from this passageShowHide
- 1How does the description of scattered ozone molecules challenge the idea of a solid shield?
- 2How do the formation and destruction of ozone show that the ozone layer is continually changing?
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About this explanatory article passage for Middle School
“Ozone Above Us: The Shield That Filters UV” is a explanatory article reading passage about The ozone layer, written for Middle School. It takes about 5 minutes to read (776 words) and comes with an interactive quiz and a printable worksheet with comprehension questions and an answer key.