600 million years ago, you wouldn't have recognized our planet. Instead of seven continents, all of the dry land existed in one supercontinent we now call Pangaea. The climate was different too, with higher temperatures and sultry humidity. Over hundreds of millions of years, the southern part of the supercontinent, called Gondwana, began to break away from the northernmost Laurasia until it sat near where Antarctica is today.

Those higher temperatures meant that plants could live, if not thrive — the continent was still on the South Pole, so vegetation had to withstand four to five months of darkness followed by four to five months where the sun never set. That meant that while modern plants take months to transition from season to season, plants on Gondwana had to transition in as little as a month if they were going to survive the rapid change in light and temperature.

The kings of the Gondwanan forest during the Permian Period were towering trees belonging to the Glosspteris genus. They grew from 65 to 131 feet (20 to 30 meters) tall and had huge, flat leaves longer than your forearm. But around 251 million years ago, disaster struck. The Permian-Triassic mass extinction killed off as much as 95 percent of Earth's species. Scientists still aren't sure what caused it, but many think that greenhouse gas emissions from volcanoes raised the planet's temperatures to hazardous levels and caused the oceans to acidify.

In reaction, the forests of Gondwana quickly fossilized. "The fungi in the wood itself were probably mineralized and turned into stone within a matter of weeks, in some cases probably while the tree was still alive," researcher Erik Gulbranson told National Geographic. "These things happened incredibly rapidly. You could have witnessed it firsthand if you were there."

That's bad news for Permian forests, but great news for us. Today, we have fossilized wood fragments and even tree trunks from the forests that once covered our coldest continent. Who needs to imagine exotic environments on other planets? We had them right here all along.

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The Permian-Triassic mass extinction wasn't the only time life on Earth died out. Learn about the other ones in "The Ends of the World: Volcanic Apocalypses, Lethal Oceans, and Our Quest to Understand Earth's Past Mass Extinctions" by Peter Brannen. The audiobook is free with a 30-day trial of Audible. We handpick reading recommendations we think you may like. If you choose to make a purchase through that link, Curiosity will get a share of the sale.