"Snowball Earth" Confirmed: Ice Covered Equator
But volcanoes would've made Earth more mud ball than snowball, scientists say.
The discovery hinged on proving that the right rocks had been covered by glaciers in the right place at the right time.
Study leader Francis Macdonald, an Earth scientist at Harvard University, and colleagues worked with volcanic rocks in Canada that were found sandwiched between glacial deposits. Such deposits are recognizable by the presence of debris left behind by melting glaciers and sediments deformed by glacial movement.
Using extremely precise uranium-lead mass spectrometry, the researchers determined that both the volcanic rocks and glacial sediments were deposited about 716.5 million years ago—during the purported snowball-Earth period.
The team then matched their findings to previous magnetic studies that had found these rocks had formed when Canada was situated near the Equator.