snowball earth roopa kamesh matt beversdorf kathy groome

Snowball EarthRoopa Kamesh

Matt Beversdorf

Kathy Groome

Theory of Snowball Earth• Continents and oceans were covered in ice approximately 600 million years ago.

• Earth was in a deep freeze, chemical cycles were halted; carbon dioxide accumulated in the atmosphere causing an extreme greenhouse effect.

• Believed to have caused the explosion of life forms seen in Cambrian fossils

Snowball Earth occurred during the Neoproterozoic

Existing Evidence• Glacial Deposits and Carbonate Caps• Paleomagnetic Studies• Banded Iron Formations• Manganese Deposits• Isotope Analysis• Plate Tectonics, Carbon Dioxide Emissions • Ice Albedo Feedback• Proterozoic Biostratigraphy: Persistence and the Explosion of Life • Extremophiles

Glacial Deposits and Carbonate Caps

Paleomagnetic Studies

From Understanding Earth, Press and Seiver, W.H. Freeman and Co.

Banded Iron Formations

Isotope Analysis

Carbon isotopes (Stanley, Steven, M., 1999)

Isotope Examples

Source: A.H. Knoll. 2000. Learning to tell Neoproterozoic Time

Albedo Effect

Once the continents were glaciated to 30 degrees latitude, there was a runaway albedo effect.

Albedo refers to the reflective ability of a material. You can see the difference in how each material reflects sunlight in the table above.

Extremophiles

Extremophiles provide evidence that life could have persisted under snowball Earth conditions.

Problems with the Snowball Earth Theory

The Explosion of Life: Just a Coincidence?

Arguments Against

• Organisms need sunlight and/or oxygen to survive (e.g. algae)

• Freeze thaw structures – no glacial deposits on a completely frozen planet

• Sea-level change – evidence for lowering of sea level

• Inconsistency of isotope results: Kennedy

• Carbon dioxide emissions - what about methane?

Alternative Theories

• Earth’s Obliquity: Increased Axial Tilt

• Slushball Earth: A variation of snowball earth where the planet did not entirely freeze. This theory is based more on climate models for the Neoproterozoic.

What do you think???