Cataclysm. Huge areas covered in red-hot volcanic glass that burned all life. Whole continents covered by ash. This and more was what Yellowstone was capable back in the Miocene.
Devastating supervolcano eruptions are one of the most extreme events that our planet has prepared for us. During a supervolcano eruption, at least a thousand times more material is ejected than during the St. Helens eruption from 1980. The problem is that we haven't found many of these eruptions in the geological record.
Thomas Knott and his colleagues from the University of Leicester tracked down two so far unknown mega-eruptions that were caused by the well-known supervolcano at Yellowstone. One of the two seems to be the largest and scariest eruptions that Yellowstone ever had. But the results of the research indicate that the supervolcano is weakening over time.
Knott's team analyzed the data using several different methods including chemical measurements, magnetic analysis, or radioisotope analysis. The key finding was that the layers of volcanic minerals in the area of the supervolcano – which we so far considered to be the result of many smaller eruptions are the result of just two colossal supereruptions which happened in the Miocene about 9 and 8.7 million years ago.
The younger of the two newly discovered supereruptions which is now called the Grey's Landing Supereruption is now the biggest volcanic event we know of that happened because of Yellowstone. And it made it into one of the three largest volcanic eruptions of all time. The researchers estimate it was about 30 % stronger than the current holder of the record – the Huckleberry Ridge Tuff.
The Grey's Landing supereruption was devastating. An area that is roughly the size of the state of New Jersey was covered in volcanic glass – destroying everything. And a gigantic amount of particles was released into the atmosphere. The whole USA and a lot of surrounding areas were being dusted by ash for a long time.
Knott's research also indicates that during the Miocene Yellowstone erupted once per roughly half a million years. But during the past three million years it seems to have erupted only twice. This seems to indicate that the capacity for eruptions decreased about three times. That is a significant decrease.
What needs to be said – the research is not that significant for how dangerous Yellowstone is. Yes, the data indicates that Yellowstone has about 900,000 years more time before it should erupt as the last time it erupted was about 630,000 years ago. So, the “fact” you might have heard that Yellowstone is already overdue to erupt is not true. Yet, supervolcanoes are fickle beasts and need to be watched carefully.
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