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 ozonedepleting 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.