New Findings Back Snowball Earth Theory
05.03.2010 - Atmosphere & Space, Water & Oceans, Ice & Snow, Flora & Fauna, Bi-polar
Reporting their findings in the journal Science, a team of geologists led by scientists from Harvard University has found evidence of sea ice reaching until the equator some 716.5 million years ago, adding new elements to support the snowball Earth theory, which theorizes that the Earth has in the past been completely covered with ice at all latitudes. This is the first time that Sturtian glaciation (the name given to that period in Earth’s history) has been shown to have occurred in the tropics, and that this glaciation lasted a minimum of 5 million years.
However, the survival of eukaryotic life (life composed of more than one cell) throughout this glacial period is a sing that sunlight and surface water remained present on Earth during this period. Even on an entirely frozen planet, ice would not form a unified layer, allowing refuges for life to form in local patches of open water. The fossil record shows all the major eukaryotic groups excluding animals were present before the glaciation. How these eukaryotes survived and whether the Sturtian stimulated evolution somehow and led to the development of animals is a question that scientists hope to further investigate.
By analyzing rocks found in Canada’s Yukon Territory, the scientists were able to find traces of glaciation, such as striated clasts, ice-rafted debris, or deformation of soft sediments. Based upon the magnetism and composition of these rocks, they believe that these rocks were located in the tropics at about 10° latitude some 716.5 million years ago.
Due to the high albedo of ice, climate modeling has predicted that if sea ice were ever to develop within 30° latitude of the equator, the whole ocean would rapidly freeze over, which strongly implies that ice would have been found at all latitudes during the Sturtian glaciation.
Scientists don’t know exactly what caused this glaciation or what ended it, however the age of 716.5 million years closely matches the age of a large igneous province stretching more than 930 miles from Alaska to Ellesmere Island in far northeastern Canada, which could mean the glaciation was either precipitated or terminated by volcanic activity.
