Why Earth Took So Long To Recover After Mass Extinction

Vast lands covered by lush forests booming with biodiversity, surrounded by monster-filled seas, in a time ruled by giants who stomped, flew, and swam across the planet — this might be the visual that comes to mind when imagining the prehistoric. For those of us who are far from scientists, scenes from Hollywood blockbusters likely shaped this picture. Because of this, it's fair to say that most of us don't have a firm grasp on what reality really looked like back then. For instance, the main characters in Universal Pictures' "The Land Before Time" lived millions of years apart — Spike the Stegosaurus and Littlefoot the Apatosaurus would have lived in the Late Jurassic Period, while pretty much every other member of the group would have lived in the Late Cretaceous (via Insider).

Other movies have taken a decent crack at portraying what other periods may have looked like, such as Studio Ghibli and Disney's "Ponyo," with its animated rendition of the Cambrian Period — which hosted the largest historical burst of evolutionary diversity (via National Geographic). And while Steven Spielberg's "Jurassic Park" certainly taught people a lot about the different species of dinosaurs, sparking a decades-long societal infatuation with them, you can probably see why that movie is not very realistic either. But us simple folk aren't the only ones left in the dark about some mysteries that have been buried in years of history (and dirt). There are some things even the scientists didn't know ... until now.

The Siberian Traps (via Live Science) released so much volcanic greenhouse gas into the atmosphere that it produced acid rain (via National Geographic). Sulfate molecules in the gas would have also blocked the sun, thus killing off marine life and decreasing biodiversity. The mass decaying of creatures also produced methane, and combined with carbon dioxide (CO2) from the Siberian Traps' eruptions, the ocean's waters became anoxic, with greenhouse conditions so extreme that they were not seen for millions of years before life took over the planet.

Although disastrous, this was just one of Earth's many mass extinctions. Over 65 million years ago, between the Cretaceous and Tertiary periods, the most famous mass extinction took place, taking out many of the world's dinosaurs that we know today. The difference between the Great Dying and this extinction, however, is that the latter mystery has primarily been solved. Based on rocks found from that age containing traces of asteroids, most scientists believe that widespread wildfires and climate change — caused by asteroids — killed the dinosaurs. As for the Permian extinction, there were still many questions left unanswered — until recently.

One species lost to the Permian extinction were a group of microorganisms called radiolarians (via Live Science). And while the loss of their presence may have not been as visibly noticeable as a Tyrannosaurus rex's, the aftershock to the ocean was drastic. But before we get into that, we have to explain the difference between processes called "chemical weathering" and "reverse weathering." 

When rocks on land break down, they release calcium into the ocean, which erodes over time and combines with CO2 to create carbonate rocks. This process of chemical weathering happens faster when the temperature is warmer, allowing for more CO2 to be released and trapped in rocks — this helps cool down the water temperature. When it gets cooler, the process slows — the CO2 is saved in the rocks to be released slowly over time and regulate the temperature from getting too cold. Reverse weathering, on the other hand, occurs when there is too much silica in the water, forming a clay that releases more CO2 than can be saved in the carbonate ocean floor rocks (seen in the chemical weathering process). And that increase in silica? That can be blamed on the little radiolarians, because when they died, they stopped doing their jobs.