Yet no such mass extinction is evident in the fossil record around Paraná, and Adriana wants to know why. She has a theory, too: perhaps the eruption around Paraná came with less toxic gases, such as sulfur, that otherwise would have killed many organisms.
So they’ve been hoping the lava-hardened rocks in Paraná hold a clue about the toxic gases like sulfur. It might sound crazy that a hard, unfeeling, uncommunicative rock could possibly tell you anything at all about the gases in the air 134 million years ago, but as it turns out, rocks surprise us.
After the bluster and trauma of an eruption is over, most of the lava cools and hardens into crystals that form a rock. Every once in a while, though, a little droplet of lava gets trapped within a crystal. Called a “melt inclusion”, this tiny once molten ball of liquid fire records the exact conditions as the eruption happened. When scientists find them millions of years later, it’s like a letter from long-ago. They can analyze that droplet of lava and get an idea of the gases that accompanied it.
Adriana and her students wanted to find these little lava droplets in Paraná — but among their 700 samples, they didn’t find a single one! It was odd.
So Adriana embarked on a different kind of hunt — a hunt from her computer. She was searching for ways to study the toxic eruptive gases without the melt inclusions. She found a paper published in 2012 by our very own Dr. Cin-Ty Lee. It gave her a different way to determine the amount of sulfur gas present 134 million years ago, when South America and Africa ripped apart, drowning Paraná in lava. Adriana didn’t need melt inclusions to apply Cin-Ty’s method. She needed more rocks from the lava.
Now it was more important than ever to gather the right rock samples. Adriana and her students had many adventures, sometimes traipsing out on dangerous railroad bridges as they moved from one rock cliff to another. “It’s a good thing we had good hearing,” Adriana recalls. They were caught by a train loaded with iron ore charging over the bridge they were walking across. “We heard a beep-beep, very loud, and we had to run as fast as we could.” Luckily, the whole team made it to a little side platform on the bridge as the train roared by.