Since the days of James Hutton, earth scientists have relied on the principle of uniformitarianism to understand past events recorded in the rock record. However, there are some events that defy analogy and boggle the mind. Chief among these is the “Snowball Earth” of the late Neoproterozoic, about 600 Ma.
In short, the Snowball Earth was a time when the entire Earth may have been covered by a sheet of ice. Then, a rapid greenhouse warming driven by buildup of carbon dioxide released the Earth from its icy tomb. This cycle was repeated many times. The evidence is attainable. Glacial deposits known as ‘diamictite’ are found mixed with marine sediments all over the globe at this time. Most startling, the continents were in the tropics! The large amount of carbon dioxide is recorded in vast deposits of limestone, the ‘cap carbonates,’ overlying the diamictite.
How does the Snowball Earth fit into the Story of Life? The timing of deposits suggests that the Snowball Earth events led to the proliferation of animals, seen in an increase in diversity of the Ediacaran biota and the onset of skeletonization.
The sample of diamictite in this case comes from the Kingston Peak Formation in the Death Valley area. The rusted red color attests to the low oxygen levels in the original environment, thus a return to the conditions that led to the deposition of banded iron formation in the oxygen-free Archaean.
Quick Links to: Introduction Oldest Rocks on Earth Oldest Fossils Prokaryotes vs. Eukaryotes Oldest Eukaryotes Oxygenation of the Atmosphere Ediacaran Fauna Snowball Earth Oldest Skeletons Pre-Cambrian/Cambrian Boundary Links for more information
