GL 107 Earth Systems Science

K. Hannula

Discussion questions for 11/12/07

1.  What are the two most abundant chemical components of Earth's atmosphere?

N₂ (nitrogen) is most abundant.

O₂ (oxygen) is second most abundant.

2.  For each of the four layers of Earth's atmosphere, describe a) the name of the layer, b) the height of the layer above Earth's surface, and c) the change in temperature with altitude.

See Fig. 16.7, p. 442 in textbook.

Troposphere: surface to 10 km (6 miles) altitude.  Temperature becomes colder as altitude becomes higher.

Stratosphere:  10 km (6 miles) to around 50 km (30 miles).  Temperature becomes warmer at higher altitude.

Mesosphere:  50 km (30 miles) to around 80 km (50 miles).  Temperature becomes colder at higher altitude.

Thermosphere:  80 km (50 miles) until the atmosphere becomes nonexistent.  Temperature becomes warmer at higher altitude.

3.  In which layer of Earth's atmosphere does most weather occur?

The troposphere.

4.  Which layer of Earth's atmosphere contains the ozone layer?

The stratosphere.

5.  What causes the "ozone hole"?

See  box 16.2, p. 441.

Chlorofluorocarbons (CFCs; compounds including freon, which was used in air conditioners and refrigerators) break down in the stratosphere.  The Cl (chlorine) acts as a catalyst for reactions that break down ozone (O₃) into O₂ and O.  (Catalysts speed reactions, but are not consumed; this is why even small amounts of CFCs create an environmental problem.)

6.  Why do seasons occur?

See Fig. 16.11 and 16.12, p. 445 in textbook.

The earth's rotation axis is tilted compared to the plane along which it travels around the sun.  During summer in the Northern Hemisphere, the Northern Hemisphere is tilted towards the sun.  During our winter, the Northern Hemisphere is tilted away from the sun.