Scientists have found evidence of ancient super-eruptions near Yellowstone National Park and are now taking a closer look at what these eruptions were like to learn a bit more about massive volcanic events.
Yellowstone is a hotbed for volcanic activity. The term "supervolcano," or "super-eruption," implies that a volcanic center has had an eruption of magnitude 8 or greater on the Volcano Explosivity Index (VEI). There are several different characteristics that allow researchers to characterize a volcano on this scale, including the volume of ejecta that is produced during an eruption and the column height during an eruption.
With that said, these super-eruptions haven't occurred for tens of thousands or even for millions of years. That's why researchers are now piecing together these volcanic eruptions by looking at the remains of the ejecta still embedded in the landscape.
In the Cassia Hills, which are located in southern Idaho, researchers have found evidence of a staggering 12 catastrophic super-eruptions. These massive eruptions left widespread glassy deposits fused to the landscape. Each of the deposits preserve different characteristics that allow them to be traced to their source.
In the latest study, the researchers analyzed the magnetic, mineralogical and chemical characteristics of the deposits found in the Cassia Hills. They uncovered records of large-scale eruptions, which caused Earth's crust in the region to actually subside by more than three kilometers. This lowering of the land left behind a deep volcanic basin along the Snake River Plain.
These older eruptions were probably hotter and more frequent than the ones that actually occurred in Yellowstone. With that said, it appears as though the entire region was prone to supervolcanic eruptions in the past.
Understanding these eruptions is extremely important for the future. This is largely because it's possible that these super-volcanoes could erupt again. With that said, scientists have calculated that the yearly probability of another caldera-forming eruption is about one in 730,000, or .00014 percent. Needless to say, these aren't large odds. This means that while it's important to understand supervolcanoes, it doesn't necessarily mean one will occur in the near future.
The findings were recently published in the journal Geological Society of America Bulletin.
