YELLOWSTONE NATIONAL PARK — The hydrothermal explosion at Biscuit Basin in Yellowstone National Park (YNP) that sent mud, water and debris spewing into the air on Tuesday, July 23 came from just below the surface, no deeper than 175 feet, scientists have found.
In a new dispatch from the Yellowstone Volcano Observatory (YVO), geologists report they have identified the type of material that was ejected in the explosion as sandstones, siltstones and gravels that lie just below the Earth’s surface. They did not find any rhyolite, indicating that the bedrock that lies a little less than 200 feet deep was not disturbed and the explosion was a shallow one.
The Biscuit Basin event was powerful, sending large boulders of up to almost two feet and weighing a hundred pounds airborne, the scientists say. The plume reached between 400 and 600 feet tall. By comparison, Old Faithful’s eruptions reach around 100 to 180 feet in the air.
Researchers are still collecting and examining debris from the Biscuit Basin explosion in order to better understand what happened. So far they say there was no detectable activity leading up to the event.
Scientists are starting to monitor more closely for hydrothermal explosions in the park, which happen about once a year and can pose a threat. These events are important to look out for due to their frequency. Damaging explosions and earthquakes can happen “several times a century,” according to YVO, whereas lava flows and small volcanic eruptions, which come from deeper underground, happen very rarely, with no such known events in the past 70,000 years.
As part of its new 2022 monitoring plan for Yellowstone, YVO is putting measures in place to try to better detect hydrothermal explosions, and potentially see warning signs of these threats before they occur. A detection station installed at Norris Geyser Basin picked up on an explosion in April, which scientists noticed after the fact.
Geologists are still working to determine the future impact of the Biscuit Basin event.
“The explosion clearly changed the shallow hydrothermal flow paths in the area, and it is unknown how the thermal features will respond,” the YVO report read.
Questions the scientists are working on include whether or not a new geyser formed and whether it looks like more activity is on the horizon for the Biscuit Basin area.
