14 DAY TRIAL // The biggest extinction in Earth history happened 251 million years ago, wiping out 90 percent of all marine species and 70 percent of all the land vertebrates. Scientists don't know for sure what caused this event and many suspect an unfortunate coincidence of several destructive factors such as volcanoes, an asteroid impact and the climate change caused by the relative recent formation of Pangea (the unified continent).
John Roth, the natural resources specialist for the Oregon Caves National Monument, has now found a black strip, made of graphite, flowing through the cream-colored marble of the Oregon Caves' walls. According to Roth, this is evidence of massive global warming caused by high levels of carbon dioxide.
"It was the biggest extinction by far of all time," he said. "Geologists and paleontologists all agree on that. [...] The extinction that killed the dinosaurs about 65 million years ago, that wasn't anything compared to this. [...] It's kind of scary that we don't know for sure what caused the worst catastrophe of life on this planet."
According to Roth, the high levels of carbon dioxide are surely at least part of the answer. It is estimated that temperatures were around 40 degrees Celsius year-round for thousands of years.
"We had a runaway hothouse effect because of the excess carbon dioxide," he said. "There was so much carbon dioxide introduced into the atmosphere, mostly from methane from the oceans. [...] That carbon dioxide build-up alone would have killed off most oxygen-breathing species."
What's interesting is that these graphite lines were not formed inside the caves - as these caves are only around half million years old. In fact, there is a pervasive graphite layer all around the globe dating back to that period and the formation of the caves has only allowed us to observe this layer but doesn't have anything to do with its formation.