Ozone Layer

What is Ozone?

• Ozone is present high in our stratosphere as a gas.

• Molecules of ozone absorb ultraviolet (UV) light emitted by our Sun.

• By shielding the Earth’s surface from most of the sun’s UV light, the ozone acts like sunscreen for all living organisms.

Ozone Creation• As ozone molecules absorb UV light they are destroyed,

therefore ozone needs to be continually replenished.• Ozone is formed throughout the atmosphere in multistep

chemical processes that require sunlight.

You can also write it as an equation…

Ozone Review

1. What is ozone made up of?

2. When UV radiation hits a molecule of ozone what happens?

3. What is the first step in ozone formation?

4. What is the second step in ozone formation?

5. Summarize how CFC’s break up ozone.

The Ozone Layer

Ozone in the atmosphere isn’t all packed into a single layer at a certain altitude above the Earth’s surface; it’s dispersed. “The ozone layer” is simply a region where ozone is more common than it is at other altitudes.

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The Dobson Unit is a way to describe how much ozone there would be in the column if it were all

squeezed into a single layer.

How much ozone compared to the rest of the atmosphere?

If all of the air in a vertical column that extends from the ground up to space were collected and squeezed together at a temperature of 0 degrees Celsius and a pressure of 1 atmosphere, that column would be 8 kilometers thick (or about 5 miles).

What are CFC’s?

• Chlorofluorocarbons (CFCs) are nontoxic, nonflammable chemicals containing atoms of carbon, chlorine, and fluorine.

• They were used in the manufacture of aerosol sprays, air conditioners in homes and cars, bug spray, paints, cleaning solvents, and other health care products.

• Scientists have estimated that a single chlorine atom from CFC can destroy 100,000 ozone molecules.

How do CFC’s destroy ozone?

The animation illustrates how one chlorine atom in the stratosphere can destroy up to 100,000 ozone molecules!

Montreal Protocol

• In 1987, 27 nations signed a global environmental treaty, the Montreal Protocol, to reduce substances that deplete the Ozone Layer.

• Reduce production levels of these compounds by 50% before the year 2000.

• Montreal Protocol

• Ozone Review Video

• Ozone Hole Video

Arctic Ozone Hole

If similar in size to the Antarctic Ozone Hole, could  expose over 700+ million people, wildlife and plants to dangerous UV ray levels. The likely hood of this happening seems inevitable based on the deterioration of

ozone layer caused by the effects of global warming on the upper atmosphere.

Arctic Ozone Hole

The Arctic ozone hole is shown in blue: The hole in the ozone layer was aggravated by colder temperatures in the stratosphere. Temperatures in the Arctic stratosphere have been dropping at an average of 1 degree centigrade a decade