Reviewing the Earth's Atmosphere - The Radiation Medium
Origin of the Atmosphere
Impacts (e.g. comets) that brought water, CO2, and other gases
to Earth in a frozen form.
Internal sources that were vented during volcanic eruptions.
Structure of the Atmosphere
The atmosphere consists of subdivisions according to temperature:
Troposphere: The lowest layer, where humans
live and weather happens. Temperature drops roughly 3.5°F
for each 1000' of elevation gain.
Stratosphere: Home of the ozone layer, which
absorbs UV radiation (heating this layer a bit).
Mesosphere & thermosphere
The Ionosphere contains plasma that absorbs
most wavelengths of radiation. Thus these wavelengths are
very hard to study from Earth itself.
images courtesy www.nasa.gov
The Ozone Layer
The Sun's UV radiation is absorbed by the ozone layer. Ozone consists
of oxygen atoms bonded in threes (O3); we breathe oxygen that's
bonded in pairs, or O2. Ozone forms in the mid-stratosphere.
Without the ozone layer, the Earth's surface would be sterilized
by UV radiation. The breakdown of the ozone layer increases skin
cancer and cataracts in humans, impairs immune systems of all animals
(including humans), and interferes with phytoplankton productivity
in the oceans.
Humans have impacted the ozone layer: Chlorofluorocarbons (CFCs)
used for refrigeration, cleaning solvents, and aerosol sprays since
the 1950s help destroy ozone. Ozone became strongly depleted over
the Earth's polar regions in the later part of the 20th century.
This video Resource: Sun Splash Ozone
This NASA video explains ozone depletion using computer graphics
and animation. An educational narrative explains how stratospheric
ozone protects us from UV radiation and demonstrates how chlorofluorocarbons
cause destruction of the Earth's ozone layer. The video is appropriate
for grades 5-8, 7 minutes in length, closed-captioned, and sells
for $10.00. It is available from NASA CORE: Visit
NASA CORE or e-mail: firstname.lastname@example.org.
Whole Body Ozone Chemistry
an activity that illustrates
the formation and destruction of ozone molecules.
The Ultraviolet Project Chemistry
an activity that uses UV
sensitive beads to illustrate the effects of the Sun's ultraviolet