Model offers one explanation for sudden change in deep-ocean chemistry almost 2 billion years ago
The collision of a large extraterrestrial object with Earth almost 2 billion years ago may have stirred the seas worldwide and delivered a small but crucial serving of oxygen to the deep ocean.
The Sudbury impact, named after the Canadian city located near the center of what remains of the ancient crater, happened around 1.85 billion years ago (SN: 6/15/02, p. 378). Despite erosion since then, the impact structure —at least 200 kilometers across — is recognized to be the second-largest on the face of the planet, says William Cannon, a geologist with the U.S. Geological Survey in Reston, Va., and coauthor on a paper in the November Geology. The event fundamentally affected the concentrations of dissolved oxygen in the deep sea — enough to almost instantly shut down the accumulation of marine sediments known as banded iron formations, report Cannon and coauthor John F. Slack, also of the USGS in Reston.