Draft 2: Snowball Earth

This topic submitted by Matt Beversdorf, Kathy Groome, Rhoopa Kamesh on 2/4/02 .

Snowball Earth Theory

Question:
What is the snowball earth theory and what evidence supports it? Also is there any evidence that does not support it?

Researchers have pieced together evidence that shows global glaciation during the neoproterozoic (900-540 Million Years Ago). Supporting data includes: paleomagnetic inclination of rocks, cap carbonates, banded iron formations, carbon isotope shifts, fossil remains, and animal evolution. These will be further discussed in a later draft.

Specific Predictions:
We predict that there is some evidence that may point to a Paleoproterozoic snowball earth. However, the evidence will not be totally conclusive.

We have found several areas of evidence for snowball earth. We have also found critisms of this theory, which we will explore at a later time.

Preliminary Research Design:
We will search the literature and internet for articles and websites that provide discussion and evidence for and against the snowball earth theory. We will make an
outline of the evidence for and against the theory. For our presentation we plan to present our outlines and open the discussion to the class. We plan to have
questions prepared to stimulate discussion among the students. At the end of the discussion, we will ask the students if the believe the theory or not, and maybe tie
the outcome of the vote to how theories are debated and accepted in the scientific world.

Literature:

Hoffman, P. F., D. P. Schrag. 2000. Snowball Earth. Scientific American. Vol. 1,

Hoffman, P. F., A. J. Kaufman, G. P. Halverson, D. P. Schrag. 1998. A Neoproterozoic Snowball Earth. Science. Vol. 281: 1342-46.

We chose these two Hoffman articles because he is one of the leading researchers in collecting data and presenting the theory.

Hyde, W.T., Crowley, T.J., Baum, S.K., and Peltier, R. 2000. Neoproterozoic ÔSnowball EarthÕ Simulations with a Coupled Climate/Ice-Sheet Model. Nature
405: 425-429

The Hyde article explains the results of a climatic model and how it relates to the snowball earth theory.

Kaufman, A.J. The Biogeochemical Aftermath of ÔSnowball EarthÕ Conditions. The University of Maryland Department of Geology, College Park, MD.

The Kaufman article explains how the changes of carbon isotopes and other chemicals deposited in rock formation can help provide evidence for the changes in biological productivity thought to occur during the global glaciation and interglacial times.

Kirschvink, J. L., E. J. Gaidos, L. E. Bertani, N. J. Beukes, J. Gutzmer, L. N. Maepa, and R. E. Steinberger. Paleoproterozoic Snowball Earth: Extereme Climatic
and Geochemcial Global Change and its Biological Consequences. Proceedings of the National Academy of Sciences. Vol. 97 (4): 1400-1405.

The Kirschvink article is similar to the Kaufman article, but delves deaper into the biological evidence and evolution during the neoproterozoic.

Websites:

Popsicle Planet. By Richard Monastersky. (http://www.sciencenews.org/sn_arc98/8_29_98/bob1html)

Wikipedia: Snowball Earth.

These two websites have good, clear summaries of the evidence for Snowball Earth

Planktonic Paradise on Slushball Earth: a Scenario for the Metazoan Radiation. By Richard Cowen. (http://www-geology.ucdavis.edu:8000/~gel3/slushball.html)

Problems with Snowball Earth Theory.
(http://irix.bris.ac.uk/~cj8639/Discussion_and_Criticism_S/Problems_with_a_snowball_earth/body_problems_with_a_snowball_earth.html)

These two websites summarize some of the critisms of the snowball earth theory. Cowen presents a similar theory based on the biological evidence.

Comings and Goings of Global Glaciations on a Neoproterozoic Tropical Platform in Namibia. By Hoffman, P.E., Kaufman, A.J., and Halverson, G.P.
(http://www.geosociety.org/pubs/gsatoday/gsat9805.htm)

This website balances the two sides, giving arguments for and against the theory.

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