YELLOWSTONE NATIONAL PARK - Last July, a powerful steam explosion rocked Biscuit Basin in Yellowstone National Park. While no one was hurt, it was a close call for some visitors and heavily damaged the nearby boardwalk.
Since then, scientists from several universities and government agencies have been studying the thermal feature and trying to determine whether it is safe to let the public return to the area.
“A huge multi-institutional group that's been studying this,” said Yellowstone Volcano Observatory Chief Scientist Dr. Mike Poland. “And we're just sort of now trying to put it back together, like investigators after some event trying to piece it back together and understand exactly what this thing looked like before it exploded.”
Thermal areas like the terraces at Mammoth and Yellowstone are always some of the park's more popular features. Biscuit Basin in the southern end of the park is not really one of the most well-known features, but it is close to a road, it has good parking and a nice boardwalk, so it has been popular over the years.
But there has been continued activity at the site since last summer.
“Small explosive events continue," Poland said. "A couple of these have been observed. There were some scientists out there pulling up some of their equipment in November, and they observed an explosion that lasted a few seconds and went about 20 or 30 feet high and threw rocks and mud, a lot of water. And then there was a tour group that was passing by on January 3rd, and they observed something very similar.”
Over the winter, Poland said, instruments left at the site detected dozens of similar explosions. A close inspection of the debris showed something very interesting.
“It’s almost like if the plumbing at your house exploded and you had pieces of the insides of the water pipes as part of the explosive debris,” Poland said.
That gives researchers a unique insight into the inner workings of these thermal sites. The underground architecture that could only be observed before by indirect ground radar, sound waves, and magnetic reflections is now laid out right on the ground.
But what’s left underground?
“We really don't know what it looks like or how it's been healing itself since that event, just because we can't see it,” Poland said.
The Park Service says Biscuit Basin will remain closed and there will be no repairs until the area is deemed safe. Last summer’s blast is also leading scientists to place seismic monitors in Biscuit Basin and other popular thermal areas.
“Lower and Midway, I think mud volcano is also worth a look," Poland said. "Places where there's a lot of people, especially during the summers, I think should be targets for these sort of monitoring, and where there's a history of some sort of explosive activity.”
Poland said the monitors don’t predict an upcoming explosion but can help scientists get an idea of where trouble spots may lurk.
“They detect low frequency acoustic energy, so not the kind of things that we hear. But because they're an array of three stations, we can use the array to determine the direction that the sound is coming from," Poland said. "So the more of these you put out, the more you can triangulate exact locations.”
