1992, J.L. Kirschvink first proposed that there were many "snowball earth" events in Neoproterozoic (850 million years ago). As you can imagine, the equator is frozen, so the whole earth is not frozen tightly and becomes a "snowball"?

Francis McDonald, a geologist at Harvard University, and his colleagues studied Canadian volcanic rocks sandwiched between glacial sediments. Scientists can identify this kind of glacier sediment by the debris left by glacier melting and the sediment deformed by glacier activity. The reddish-brown ice age sediments prove that this Canadian volcanic rock was covered with ice and snow in the era of "Snowball Earth".

MacDonald's team determined that volcanic rocks and glacial deposits were deposited about 765,438+06 million years ago by using extremely accurate uranium-lead radioactive dating. Next, the researchers compared their findings with a series of previous studies, which found that volcanic rocks were formed near the equator in Canada. As time goes by, the activity of tectonic plates drives volcanic rocks to move northward and reach the Yukon and northwest of Canada.