13-2 The Ozone Shield Page 335. A. Chemicals that Cause Ozone Depletion 1. The ozone layer is an area in the stratosphere where ozone is highly concentrated.

13-2 The Ozone Shield

Page 335

A. Chemicals that Cause Ozone Depletion

• 1. The ozone layer is an area in the stratosphere where ozone is highly concentrated.

A. Chemicals that Cause Ozone Depletion

• 2. Ozone is a molecule made of 3 oxygen atoms (O3) and absorbs ultraviolet (UV) rays that can harm living cells.

A. Chemicals that Cause Ozone Depletion

• 3. Human-made chemicals called chloroflurorocarbons (CFC’s) are damaging the ozone layer.

A. Chemicals that Cause Ozone Depletion

• 4. CFC’s are inexpensive to make and used in items such as coolants, paint, and deodorant.

A. Chemicals that Cause Ozone Depletion

• 5. On the earths surface, CFC’s are stable. In the atmosphere CFC’s break apart.

A. Chemicals that Cause Ozone Depletion

• 6. The chlorine atoms from CFC’s breakdown ozone in the stratosphere.

A. Chemicals that Cause Ozone Depletion

• 7. Estimates show that 1 chlorine atom can break down up to 100,000 ozone molecules.

B. The Ozone Hole

• 1. A thinning of stratospheric ozone that occurs over the poles during the spring.

B. The Ozone Hole

• 2. In 1985, scientists in Antarctica found the ozone layer over the south pole was thinned by 50-90%.

B. The Ozone Hole

• 3. Scientists and governments have been working together world wide and the ozone in the stratosphere has stopped declining.

C. How Does the Ozone Hole Form?

• 1. During the dark polar winter, winds over Antarctica (called the polar vortex), isolate cold air from warm air.

C. How Does the Ozone Hole Form?

• 2. When air in the vortex falls below -80°C clouds made of water and nitric acid, called polar stratospheric clouds, start to form.

C. How Does the Ozone Hole Form?

• 3. CFC’s enter the clouds and are broken down into chlorine atoms that combine with UV rays and for ozone holes that last several months.

D. Effects of Ozone on Living Things

• 1. ↓Ozone= ↑ UV Radiation• 2. 2. UV damages DNA, which can lead to skin

cancer.

D. Effects of Ozone on Living Things

• 3. UV kills phytoplankton which disrupts aquatic food chains and increases CO2 in the atmosphere.

D. Effects of Ozone on Living Things

• 4. UV interferes with photosynthesis, damaging plant life.

E. Protecting the Ozone Layer

• 1. 1987: Group of nations met in Canada and formed the Montreal Protocol to limit production of CFC’s.

E. Protecting the Ozone Layer

• 2. A 2010 study showed that many ozone-depleting Substances (ODS) have been phased out.

E. Protecting the Ozone Layer

• 3. Scientists are still searching for ways to protect the ozone layer because CFC’s may remain active in the atmosphere for 60-120 years.