The document describes the key characteristics of Earth's atmosphere. It discusses the composition of the atmosphere, the different layers including the troposphere, stratosphere, mesosphere and thermosphere. It then covers the origin of the atmosphere from outgassing, the appearance of oxygen through photosynthesis, and how human activities have impacted levels of carbon dioxide and ozone over time.

1. Characteristics of the
Atmosphere

2. Characteristics of the Atmosphere
• 1. The Astmosphere
– a. The atmosphere is a layer of gases and
tiny particles that surrounds the earth
– b. The study of the atmosphere is called
meteorology
• i. Meteorologists study
• 1. Weather - the general condition of the
atmosphere at a particular time and place
• 2. Climate - general weather conditions
over many years
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3. Characteristics of the Atmosphere
• 2. Composition of the Atmosphere
– a. Most abundant gases
• i. Nitrogen = 77%
• ii. Oxygen = 21%
• iii. Argon = .93%
– b. Most abundant compounds
• i. Carbon Dioxide- from volcanoes and
human activity
• ii. Water Vapor- from photosynthesis and
transpiration
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4. Characteristics of the Atmosphere
• 3. Layers of the Atmosphere
– a. Troposphere
• i. The layer closest to the Earth’s Surface. The
Weather Layer
• Ii. Closest to earth where water vapor & carbon
dioxide are found
• iii. Temperature decreases as altitude increases.
• iv. Tropopause: zone at the top of the troposphere
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5. Characteristics of the Atmosphere
• b. Stratosphere (aka the Ozone
Layer)
i. Atmospheric layer that extends up from
the tropopause
ii. Almost all of the ozone is concentrated
here
iii. As altitude increases, temperature
increases slightly
iv. Heated by UV absorption
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v. Stratopause: zone at the upper boundary

6. Characteristics of the Atmosphere
• c. Mesosphere
i. Atmospheric layer above the
Stratosphere
ii. The coldest layer, dropping to a
temperature of -90 degrees C
iii.Temperature decreases as
altitude increase
iv.Mesopause: upper zone of the
mesosphere 6

7. Characteristics of the Atmosphere
• d. Thermosphere
i. Atmospheric layer above the
Mesopause
ii. Temperature increase with altitude
iii. Air is to thin, no temperature is known
iv. Lonosphere: lower region of the
atmosphere
v. Exosphere: the zone of indefinite
altitude (outer most)
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8. Characteristics of the
Atmosphere
• 3. Atmospheric Pressure
– a. Density of the air affects the pressure
i. Less dense (lighter weight of air) = lower
pressure
ii. More dense air = higher pressure
a) The atmosphere’s pressure falls as you
climb in altitude
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9. Characteristics of the
Atmosphere
• 1. Origin of the Earth’s Atmosphere-
Hydrogen & Helium escaped!!
a. They are the most abundant elements in the
Universe
– Because they are small & light, they move
fast
– Since the earth is so small compared to the
universe, Hydrogen & Helium escaped it’s
atmosphere long ago
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10. Characteristics of the
Atmosphere
• 2. Outgassing: the atmosphere was
built up by release of gasses, mostly
from Volcanoes!
a. Water vapor and carbon dioxide built up first
b. Small amounts of nitrogen were released
c. NO oxygen was given off
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11. Characteristics of the
Atmosphere
• 3 Variations in Carbon Dioxide
Concentrations
– a. In the beginning, carbon dioxide was in
abundance
– b. Over time, the following changes
happened:
i. Water vapor condensed to form oceans
ii. Carbon dioxide dissolved in oceans and became
carbonate rock
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12. Characteristics of the
Atmosphere
• 4. Atmospheric Oxygen Appears…
a. Oxygen was released when plants formed
b. Plants & algae used carbon dioxide to go
through photosynthesis and release oxygen
gas into the atmosphere
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13. Characteristics of the
Atmosphere
• 5. Atmospheric Evolution- the
atmosphere is dynamic and evolving!!
a. Water vapor continues to condense into the oceans
b. Carbon dioxide is continuously “locked up” into
rocks
c. Oxygen is continually formed from photosynthesis
in plants
d. Human activity (burning fossil fuels and agriculture)
changes the atmosphere’s composition
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14. Characteristics of the
Amtosphere
• 1. The Ozone Layer!!
a. Ozone forms in the stratosphere
b. Ozone is oxygen that absorbs ultraviolet
(UV) rays so they don’t reach the ground…
this made “life on earth” possible
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15. Characteristics of the
Atmosphere
• 2. Human Activity affects the natural
amount of ozone that forms
a. Harmful gasses are emitted in large amounts from
industry and agriculture
b. CFC’s are emitted from other human “inventions”
and break down the ozone: refrigerators, exhaust,
air conditioners, aerosols
c. Small particles replace the oxygen in the ozone
layer when released: pollution, volcanic dust,
burning of rainforests
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16. Characteristics of the
Atmosphere
• 3. Variation in oxygen (ozone)
amounts
a. Some natural processes (animals &
weathering of rocks) use up oxygen
b. Human activity also uses up oxygen
– Oxygen is also released by land and ocean
plants during photosynthesis
– Ozone amounts will remain constant if the
amount used up equals the amount
produced
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