Ozone-layer

noun
1.
Meteorology. the layer of the upper atmosphere where most atmospheric ozone is concentrated, from about 8 to 30 miles (12 to 48 km) above the earth, with the maximum ozone concentration occurring at an altitude of about 12 miles (19 km).
noun
1.
the region of the stratosphere with the highest concentration of ozone molecules, which by absorbing high-energy solar ultraviolet radiation protects organisms on earth Also called ozonosphere
ozone layer
A region of the upper atmosphere containing relatively high levels of ozone, located mostly within the stratosphere, with the greatest concentrations occurring from about 15 to 30 km (10 to 19 mi) above the Earth’s surface. The ozone absorbs large amounts of solar ultraviolet radiation, preventing it from reaching the Earth’s surface. The concentration of ozone in the ozone layer is usually under 10 parts per million. Also called ozonosphere. See Note at ozone.

A band of ozone in the upper atmosphere. Ozone is a molecule made of three atoms of oxygen instead of the usual two.

Note: The ozone layer absorbs harmful ultraviolet radiation from the sun and is thus very important to the health of human beings and other life forms on Earth. The Earth’s ozone layer could be at risk because of the action of chlorofluorocarbons, but international treaties have banned the production of these chemicals. The ozone layer is expected to return to normal in a few decades. (See ozone hole.)