Unformatted text preview: ts Some ages less certain than others 25 2/19/2008 Tillites and cap carbonate Glacial deposits, tillites, are a mixture of different sediment sizes and types (unsorted, unstratified) Tillites are directly overlain by carbonate rocks - This is uncommon to have such a fast transition (Implies very cold then very hot conditions--see next slide) Cap C carbonate b t Glacial deposit (tillites) The CO2 cycle as a thermostat
CO2 is more soluble in colder water CO2 is less soluble in warmer water Carbonate minerals form faster at higher ocean temperatures
Thus If Earth warms up a bit, carbonate minerals form in the oceans at a more rapid rate If the Earth cools a bit, carbonate minerals form more slowly in the oceans.
http://www.elmhurst.edu/~chm/ vchembook/174temppres.html 26 2/19/2008 BIFs back? In the first snowball event, banded iron formations occur (not seen since ~ 2.3 Ga!) The Freeze-Fry: The Freeze FreezeLongLong-term carbon cycle becomes imbalanced c cle Large land areas clustered at low latitudes--but latitudes-- they still spread to higher latitudes Would have increased albedo less overall energy retained Photosynthesis continues to draw down CO2 Weathering continues to draw down CO2 As atmospheric levels of CO2 levels decrease, decrease, so do global temperatures on Earth This leads to more ice inc. albedo more ice, etc.
A positive, reinforcing feedback 27 2/19/2008 The Freeze-Fry: The Fry FreezeCO2 imbalance in oth...
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- Spring '08
- Geology, Cambrian, Cambrian Explosion, Snowball Earth, Ediacaran fauna