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Sea ice may have cover the Earth ’s surface all the way to the equator hundreds of millions of years ago , a new work retrieve , adding more evidence to the theory that a " snowball Earth " once existed .
The determination , detail in the March 5 military issue of the journal Science , also has implications for the survival andevolution of lifeon Earth through this bitterice age .
Glaciation at tropical latitudes provides evidence of a “snowball Earth."
geologist found evidence that tropic areas were once cover by glacier by examining ancient tropical rocks that are now ground in remote northwestern Canada . These rocks have go because the Earth ’s control surface , and the rocks on it , are in unceasing movement , pushed around by the roiling stream of the planet ’s DoI , a cognitive process call plate tectonics ) .
The rocks from Canada ’s Yukon Territory showed glacial deposits and other signs of glaciation , such as striated clast , ice rink - rafted detritus , and deformation of soft deposit .
The scientist were capable to determine , based on the magnetism and composition of these rocks , that 716.5 million years ago the rock were located at sea - stage in the tropics , at about 10 degree latitude . The period of glaciations that pass then is telephone Sturtian glaciation , one of the two greatest glass age known to have taken place on Earth .
" This is the first metre that the Sturtian glaciation has been shown to have occurred at tropical latitudes , providing unmediated evidence that this especial glaciation was a ' snowball Earth ' event , " said lead generator of the study Francis Macdonald , a geologist at Harvard University .
" Our data also suggest that the Sturtian glaciation lasted a lower limit of five million years , " Macdonald tot up .
One intriguing dubiousness suggest by the determination is how biography form — especially those more complex than microbes — survived throughout this harsh climate . Their survival of the fittest suggest that sunlight and aerofoil water remain uncommitted somewhere on Earth ’s Earth’s surface , perhaps in patches of open water that shape in the sea chicken feed and provided a refuge for life .
" The fossil record suggest that all of the major eukaryotic chemical group , with the potential exception of beast , existed before the Sturtian glaciation , " Macdonald order . " The questions that arise from this are : If a snowball Earth survive , how did these eukaryotes survive ? Did the Sturtian snowball Earth stimulate organic evolution and the origin of animals ? " ( eukaryote have a true nucleus and are more complex than so - called prokaryote . )
" From an evolutionary position , " he tote up , " it ’s not always a bad thing for life on Earth to confront severe tenseness . "
Scientists do n’t know exactly what have this glaciation or what ended it , but Macdonald enjoin its old age of 716.5 million years intimately match the age of a large igneous province – made up of rocks formed by magma that has cool down – stretch more than 932 miles ( 1,500 kilometers ) from Alaska to Ellesmere Island in far northeastern Canada .
This conjunction could intend the glaciation was either precipitated or terminated by volcanic activity .
The work was plunk for by the National Science Foundation and the Polar Continental Shelf Project .
