Tectonics and Climate 2 Flashcards
(10 cards)
What are the most recent hothouse climate and icehouse climates?
Hothouse Climate
- 65 - 260 m.y. ago (Dinosaur era)
Icehouse Climate
- since 65 m.y. ago (present)
(How did atmospheric CO2 change over time in the Cambrian period?)
What is the Seafloor Spreading Rate Hypothesis? (BLAG)
BLAG Hypothesis
- changes in the globally average rate of seafloor spreading has controlled the delivery of CO2 to the atmosphere
(BLAG Hypothesis)
How does CO2 get expelled from the crust?
- most CO2 is expelled by volcanic activity at plate boundaries (convergent, divergent)
- less CO2 is expelled by volcanic hotspots (not affected by seafloor spreading)
(BLAG Hypothesis)
How does a faster spreading seafloor rate increase the amount of atmospheric CO2?
- when seafloor spreading rates are faster, large amounts of new crust are created at mid-ocean ridges due to releases of magma, delivering greater amount of CO2 to the atmosphere
- there is more rapid subduction of crust and sediment in ocean trenches, more melting of the crusts into magma and release of CO2 through volcanoes
(BLAG Hypothesis)
What is the Chemical Weathering Feedback?
Chemical Weathering (Negative Feedback)
- due to higher temperature, causes higher evaporation and precipitation
- denser forests and more photosynthesis
- increased chemical weathering, hence more CO2 removal
- reduced effects of warming
Net cooling effect
(BLAG Hypothesis)
What are the problems with the BLAG Hypothesis?
- increasing oxygen isotope in the deep waters, evidencing a deep water cooling
- global spreading rate has increased since 15 m.y. ago, but Earth is currently still cooling
(How did atmospheric CO2 change over time in the Cambrian period?)
What is the Uplift Weathering Hypothesis?
- global mean rate of chemical silicate weathering is caused by surface rock exposure
- an increase in rock exposure can enhance chemical weathering through climate agents (temperature, precipitation, vegetation), reducing CO2
- limestone weathering, NO granite weathering
uplift is caused by inter-continental collisions (e.g. India and Asia)
(Uplift Weathering Hypothesis)
What are the different ways CO2 is removed?
- Mass Wasting
- steep slopes have active erosion, including rocks sliding, debris flow
- this causes exposure of fresh bedrock - Mountain glaciers grinding rock
- rock breaks down, smaller rocks have larger surface area - High precipitation at steep slops
- heavy precipitation favours chemical weathering - Earthquakes
- common in mountain region
- disrupt rocks and increase rock fragmentation
(Uplift Weathering Hypothesis)
What is the negative feedback of uplift weathering?
- when there is uplift and weathering increases, there are lower CO2 levels and global cooling
- lower temperature in in regions not uplifted, less precipitation, temperature and vegetation
- chemical weathering reduces, leading to less CO2 removal
Reduced cooling effect
(How did atmospheric CO2 change over time in the Cambrian period?)
What is the Ocean Gateway Hypothesis?
- Opening of Drake’s Passage (40 - 30 m.y.)
- when the passage was opened, led to a strong Antarctic circumpolar current
- prevents warm poleward currents to transport heat to Antarctica
- does not fully explain - Closure of Isthumus of Panama (4.3 m.y.)
- water unable to cross from Atlantic Ocean to Pacific Ocean
- Atlantic Ocean becomes salter, warm salty water moves northwards and transfers heat to Europe
- moisture brought to Europe will precipitate as snow at the North American continents
