Lec 2 - Atmosphere, CO2, Tectonics, Climate

Question 1

How thick is the atmosphere?

Answer 1

200-400km
relatively thin compared to Earth diameter!

Question 2

What are the layers of the atmosphere, from the ground up?

Answer 2

• troposphere
• stratosphere
• mesosphere
• thermosphere

Question 3

What defines the layers of the atmosphere?

Answer 3

• the Temperature Profile (change in temperature with height)
• pauses in temp profile at the start of each layer
• ‘inversions’ in the direction of temperature change

Question 4

In what atmospheric layer does most weather occur?

Answer 4

troposphere

Question 5

How does the thickness of the troposphere vary?

Answer 5

• 8-10km at poles, 16km over tropics
• due to thermal expansion

Question 6

What causes the inversion in the temperature profile of the Stratosphere?

Answer 6

absorption of UV radiation by ozone, causing hot air to rise

Question 7

What is the coldest atmospheric layer?

Answer 7

mesosphere - radiation absorption only occurs in the bottom layer

Question 8

What is the atmosphere made of?

Answer 8

• gases
• suspended particles (aerosols)
• liquid/solid water

Question 9

How well are gases mixed in the atmosphere?

Answer 9

• <80km = well-mixed (homosphere)
• > 80km - separated by gravity (heterosphere)

Question 10

What are the permanent gases of the atmosphere?

Answer 10

• N
• O
• Ar
• Ne
• He
• K
• Xe
• H

Question 11

What are the main variable gases of the atmosphere?

Answer 11

• water
• CO2
• O3
• methane

Question 12

What classifies a gas as permanent/variable?

Answer 12

residence time = reservoir size/flux rate

Question 13

How abundant is water in the atmosphere?

Answer 13

• ranges from 0-5% of air

Question 14

How much of the atmosphere is CO2?

Answer 14

0.039%

Question 15

How is CO2 added to the atmosphere?

Answer 15

respiration, volcanic activity, decay, combustion

Question 16

How is CO2 removed from the atmosphere?

Answer 16

• photosynthesis
• long term: weathering

Question 17

What does ozone do in the atmosphere?

Answer 17

• pollutant in lower atmosphere
• absorbs UV radiation in upper atmosphere

Question 18

How is methane released into the atmosphere?

Answer 18

fossil fuels, livestock, digestion, agriculture (esp rice)

Question 19

What are the two main types of continental chemical weathering?

Answer 19

• hydrolysis
• dissolution

Question 20

What controls chemical weathering rates?

Answer 20

• temp increases
• precipitation increases
• temp/precipitation impact vegetation/productivity

Question 21

What kind of feedback is chemical weathering?

Answer 21

negative loop

Question 22

What kind of feedback loop does water vapour cause?

Answer 22

• positive feedback!
• more water = GHG Effect, so more heating = more evaporation = more water in atmosphere

Question 23

What is the Gaia hypothesis?

Answer 23

• living things regulate climate
• based on CO2 cycle, photosynthesis affecting weathering, and plankton storing CO2 in shells

Question 24

What is the polar position hypothesis?

Answer 24

• the position of continents determine ‘ice house’ intervals
• suggests ice sheets should appear on continents near polar latitudes, and no ice sheets should appear outside of these latitudes
• BUT - based on records, not all continents in polar positions develop ice sheets (ex Pangaea - CO2 compensates for weaker sun, no ice!)

Question 25

How could tectonics control CO2?

Answer 25

• Volcanoes - add CO2
• weathering - remove CO2

Question 26

What is the BLAG Hypothesis?

Answer 26

• most CO2 in atmosphere is expelled from margins of converging plates (volcanoes), and divergent plates (ocean ridges)

Question 27

Why is there more weathering with more uplift?

Answer 27

• mass wasting
• earthquakes
• steep slopes
• heavy precipitation
• glaciers

Question 28

How might uplift weathering be a feedback?

Answer 28

more uplift weathering means more CO2 removal, but as rocks in other areas age, they remove less and less CO2. Maybe these two effects balance out?