snowball earth Flashcards
1
Q
what is runaway feedback?
A
- cooling leads to ice advance
- more ice reflects more sun
- less sunlight absorbed
- more cooling
- more ice advance
- once ice crosses a critical latitude (-30°C) causes runaway = snowball earth
2
Q
when did snowball earth happen?
A
2220 Ma then 710 Ma then 640 Ma
3
Q
what evidence is there for snowball earth?
A
- paleomagnetism
- rocks contain compasses frozen when they are deposited
- sediments deposited in horizontal layers
- the dip of the compass relative to the horizontal tells us how near/far from the equator the rock was
4
Q
what amplified CO2 build up?
A
reverse ice-albedo feedback
5
Q
what are cap carbonates?
A
mixing a high CO2 atm with an ocean full of alkaline ions eg. Ca2+ to form carbonates
6
Q
when do cap carbonates occur?
A
right after glaciations
7
Q
what triggered snowballs?
A
- the break up of supercontinents eg. Rodinia
- caused basalt outpouring which created a highly weatherable surface
- increased runoff promoted high weathering rates and CO2 drawdown
8
Q
what caused the Neoproterozoic glaciations?
A
increased silicate weathering cooled the planet
