Supercontinent Pangea Gets Climate Rethink

July 28, 2008 -- Once thought temperate, the climate on Earth 300 million years ago may have gotten far colder than scientists ever suspected.

Scientists tend to think that life on the great supercontinent Pangea enjoyed weather that was similar to today's. With an ice sheet dominating the landscape near the south pole, there was certainly an occasional cold snap, but the tropics are believed to have been hot and humid.

Gerilyn Soreghan of Oklahoma University and a team of researchers are now questioning that belief. They've found evidence that a massive glacier lived near the equator, further south and closer to sea level than thought possible.

If true, the discovery implies the climate during the late Paleozoic Era was even chillier than during the last Ice Age. It could also have been extremely volatile, swinging in wild cycles back and forth between frigid and balmy over millions of years.

Glacial deposits and changes in ancient sea level show that ice probably ebbed and flowed through a series of Paleozoic Ice Ages, much as it has in recent geologic history, with the last cold snap around 20,000 years ago.

Even during the worst of the last Ice Age, though, Earth's tropics stayed relatively mild. Any glaciers near the equator would have melted if they descended below altitudes of around 3,400 to 4,400 meters (11,145 to 14,440 feet) above sea level.

The same was thought to be true for Pangean times, until Soreghan discovered strange rocks hiding out on the floor of the remote Unaweep Canyon, high on the Colorado Pleateau.