April 21, 2008 7:29 PM Subscribe
In 1987, the Caltech biomagnetist and paleomagnetist Joe Kirschvink gave undergraduate Dawn Sumner a rock sample [from South Australia] to study for her senior thesis. The apparent glacial origin of this rock lead directly to the theory that periodically the Earth has been thoroughly glaciated from the poles to the Equator: the so-called Snowball Earth events. A website dedicated to this theory includes detailed teaching slides, a FAQ, and many other resources on this interesting period in Earth's history.
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