Significant global variability in climate can be traced back into the Paleozoic era when an explosion of multicellular life took place within the oceans. There is recent evidence of a possible early snowball earth episode that occurred as a result of the Great Oxygenation event as early as 2.4-2.1 million years ago in the Paleoproterozoic era. A snowball earth is a hypothetical scenario that some scientists suggest could have occurred at least once in Earth’s record, where the entire or nearly entire Earth was covered in ice. An explosion of anaerobic organisms producing oxygen as a by-product is thought to have lowered methane levels in the atmosphere. Because solar activity was lower than modern times (Early Sun Paradox), it was thought that lowering of methane, a greenhouse gas, would ultimately reduce global temperatures leading to the snowball earth. Many pro-snowball earth scientists believe that these types of events likely occur due to a positive feedback effect. Once, global temperatures sufficiently cooled, a runaway effect would occur that would keep global temperatures in a decline. However, there is still a great amount of disagreement between scientists in regards to the Huronian glaciation which could be the longest lasting glacial period in earth’s history.
Scientists have found some evidence to support the case of the Huronian glaciations to have covered the entire Earth as such. Such evidence is that the global distribution of Sturtian and Marinoan glacial deposits, suggest at this geologic time, that most land mass were indeed covered in a glacier. The warmer parts of the surface ocean during this time contain glacial marine deposits and thick limestone type rock which suggest a much colder regime. Further, paleomagnetic data suggests that glacial sediment has been found near the paleo-equator, or the location of the equator during this geologic time.
However, some evidence would seem to suggest that snowball earth was non-existent. Such evidence comes from rocks in Oman, that have produced evidence of many cycles of hot and cold regimes in the Paleoproterozoic era’s. Other evidence against this hypothesis is that the global deposits of glacial marine sediment are not the same age everywhere which would seem to suggest that the collective nature of all the global glacial sediment was not deposited in a single time that a snowball earth would produce. Finally, indications of an open ocean during this time do exist. Indications of open water such as biomarkers of phototrophism, numerous examples of wave ripples and ice rafted debris have been found to travel extensive distances across the paleo-oceans. While arguments still exist in whether the Earth was completely covered in ice, it is always interesting to think about how different Earth’s climate could have been.
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© 2018 Meteorologist Allan Diegan