Lecture 4: Out of the Snowball Flashcards
What was the late Proterozoic?
The cryogenian and ediacaran period
What was the Proterozoic supercontinent?
Rodinia begins to break up
What happened beneath the ice?
The continents continued to break apart.
Magma erupted at shallow water mid-ocean ridges into cold seawater.
Produced volcanic glass (hyaloclastile) -> can get altered very quickly + leaches sons into the ocean
Alkalinity soared.
How to thaw the freezer?
Volcanic eruptions (CO2) No rain to wash CO2 out of atmosphere
What was the big melt?
Temperatures soared from -50 degrees -> 40-50 degrees in only a few hundred years.
Temp contrast between equator and poles = hyper canes
Ice melt = water vapour returned (greenhouse gas) = clouds
What did all the rain from the big melt mean…?
Hundreds of years of ACID rain = rapid erosion.
HCO3- washed into oceans, combines with Ca2+ and Mg2+ and makes limestone CaCO3.
How did life survive the freezer?
Refugia: Equatorial seas Hot springs/ vents Brine channels Beneath sea/ lake ice
How did glaciations change the planet?
Atmospheric O2 levels jump
Plankton diversifies rapidly
Multicellular animals appear
What happened as a result of accelerated continental weathering during the late Proterozoic?
Accelerated continental weathering, more river run off
Co2 in rain weathers rocks -> produces bicarbonate ions (HCO3-) which goes into oceans and increases biological productivity.
What did the bicarbonate ions (HCO3-) that went into oceans and increased biological productivity produce?
Organic componunds (org C locks in rocks).
What did the production of organic componunds (org C locks in rocks) in the ocean cause?
CO2 atm conc drops, climate cools
Runaway icehouse feedback loop
Most atmospheric water vapour was snowed out and locked in ice -> virtually no clouds and oceans stagnated under ice cover-> anoxia
Tipping point needed how much of todays CO2 atm conc to start melt?
350x
