Scientists are taking a closer look at how rivers of hot ash and gas move when a superevolcano erupts. They've gained further insight into what may happen when a supervolcano explodes.
In this latest study, the researchers focused on the Silver Creek caldera, which sits at the intersection of California, Nevada and Arizona. When this supervolcano erupted 18.8 million years ago, it flooded parts of all three states with river-like currents of hot ash and gas called pyroclastic flows. These tides of volcanic material traveled for more than 100 miles.
The researchers combined recent lab experiments with field data from the 1980s, some of which was captured in colorful Kodachrome slides. This revealed that the rivers of ash and gas emanating from the Silver Creek caldera likely traveled at modest speeds of about 10 to 45 miles per hour.
"Intuitively, most of us would think that for the pyroclastic flow to go such an extreme distance, it would have to start off with a very high speed," said Oliver Roch, the co-author of the study. "But this isn't consistent with what we found."
Research on pyroclastic flows is important. This is largely because it can help inform disaster preparedness efforts.
"We want to understand these pyroclastic flows so we can do a good job of forecasting the behavior of these flows when a volcano erupts," said Greg A. Valentine of the University at Buffalo. "The character and speed of the flows will affect how much time you might have to get out of the way, although the only truly safe thing to do is to evacuate before a flow starts."
The new study favors one of two competing theories about how pyroclastic flows are able to cover long distances. In this case, the research supports the theory that states that the flows should be dense and fluid-like, with pressurized gas between ash particles. The researchers also found that the ancient pyroclastic flows must have been moving about 10 to 45 miles per hour in order to pick up rocks that the researchers found were shifted.
The findings could have widespread applicability when it comes to understanding supervolcanoes.
