Chapter 5 - Tectonics and Long Term Climate

Question 1

Why was the polar position hypothesis introduced?

Answer 1

To explain changes between warm greenhouse climates and cold icehouse climates in the last 500 million years.
Proposes latitudinal position as a likely cause of continental glaciation

Question 2

What are the problems associated with continental movement plotted by polar wander?

Answer 2

• 445 mya polar ice was very brief - does not match with slow movement of Gondwana across the South pole
  Lack of glaciations between 425-325 despite Gondwana landmass at south pole (Argues against polar position as the only requirement)

Question 3

Most CO2 expelled to atmosphere at?

Answer 3

convergent (Subduction) and divergent (MOR) margins, hot-spots and via oxidation

Question 4

What is the uplift weathering hypothesis?

Answer 4

Proposes uplift accelerates chemical weathering through listed factors below
Faster weathering = more co2 draw down (and vice versa)

Question 5

How does palaeomagnetism tell us about latitudes of past continents?

Answer 5

Through the degree of inclination of remnant magnetism. Basaltic rocks which cool at high latitudes have a steep angle while those cooled near the equator have a more horizontal internal compass.

Question 6

Explain how palaeomagnetism tells us about spreading rates

Answer 6

Magnetic lineations give information about spreading rates. These occur either side of MOR and are equal both sides (also contain info about magnetism). Lineations can be dated and restore continents to past positions

Question 7

Do glaciations always occur when continents are in polar positions?

Answer 7

No. contrary to the polar position hypothesis, latitude is not the only requirement for glaciations to occur. Other conditions include low atmospheric co2 levels, setting up a positive feedback system, and sufficient moisture to replenish ice which melts at the margins

Question 8

Major characteristics of the climate of Pangaea?

Answer 8

“Super-monsoons” due to vast landmass, interior was likely very arid, humid coastal regions

Question 9

What is the central concept behind BLAG?

Answer 9

Central idea is that changes in the rate of seafloor spreading control flux of co2 into the atmosphere, thus account for the greenhouse to icehouse variations seen in the past.

Question 10

How could chemical weathering be both a driver and thermostat of Earths climate?

Answer 10

It is a thermostat because of negative feedback. Increased global warming increases precipitation and thus chemical weathering. This draws down co2 from the atmosphere, slowing down warming. In contrast, global cooling reduces chemical weathering therefore leaving co2 in the atmosphere to relieve cooling effects.
However the uplift weathering hypothesis suggests that chemical weathering is increased during uplift and exposure of new rock, thus driving climate change through lowering co2