Surprise Yellowstone geyser eruption highlights little known hazard at popular park
BILLINGS, Mont. — a surprising outburst The steam that erupted from a geyser basin in Yellowstone National Park, sending people scrambling for safety as large rocks were shot into the air, has highlighted a little-known danger that scientists hope to one day be able to predict.
Tuesday’s hydrothermal explosion in Biscuit Basin caused no injuries as dozens of people fled along the boardwalk before the wooden walkway was destroyed. The explosion sent steam, water and dark-colored rocks and soil an estimated 100 feet into the air.
It came in a park filled with geysers, hot springs and other hydrothermal phenomena that attract millions of tourists each year. Some, like the famous Old Faithful, erupt like clockwork and are well understood by the scientists who monitor the park’s seismic activity.
But the type of explosion that occurred this week is less common and less well-known, and potentially more dangerous because it occurs without warning.
“This underscores that even small events — and this one was relatively small in the grand scheme of things, although dramatic — can be really dangerous,” said Michael Poland, chief scientist at the Yellowstone Volcano Observatory. “We’ve gotten pretty good at understanding the signals that a volcano is waking up and might erupt. We don’t have that knowledge base for hydrothermal systems like Yellowstone.”
Poland and other scientists are trying to change that with a nascent monitoring system recently installed in another Yellowstone geyser basin. It measures seismic activity, deformations in the Earth’s surface and low-frequency acoustic energy that could signal an eruption.
The day before the Biscuit Basin explosion, the US Geological Survey published a paper by observatory scientists about a smaller hydrothermal explosion in April in Yellowstone’s Norris Geyser Basin. It was the first time such an event had been recognized from monitoring data, which was closely examined after geologists discovered a small crater in the basin in May.
The two explosions are believed to have been caused by blocked passages in the vast natural plumbing system beneath Yellowstone, Poland said. A blockage can cause the heated, pressurized water to instantly turn to steam and explode.
Tuesday’s explosion came with little warning. Witness Vlada March told The Associated Press that steam began to rise in the Biscuit Basin “and within seconds it became this huge thing. … It just exploded and became like a black cloud covering the sun.”
In March, the explosion was filmed in many places, with debris flying through the air and tourists fleeing in fear.
“I think our guide said, ‘Run!’ And I started running and I started yelling at the kids, ‘Run, run, run!’” she added.
According to Poland, scientists don’t know if they can find a way to predict the explosions.
Yellowstone is home to the caldera of a massive, dormant volcano that shows no signs of erupting, but which provides the heat for the national park’s famous geysers, hot springs, mud pots, and several other hydrothermal features. While far less common than geyser eruptions, hydrothermal explosions occur frequently enough in Yellowstone to warrant study—and pose a safety risk.
For a geologist, it’s a payoff to see one in person. That happened in 2009, when Montana Tech geology professor Mike Stickney and several other geologists were nearby when one happened near the site of Tuesday’s explosion in the Biscuit Basin.
“It was very sudden and without any warning, just standing there on the boardwalk. It was just a ‘whoosh’ and it was done. Nobody saw it coming,” Stickney said.
Although the sensitive seismometer at Old Faithful, a few miles away, did not register the explosion, it estimated that the recent explosion was ten times larger.
In May, scientists discovered a crater several feet (1-2 meters) wide in the Norris Geyser Basin, 18 miles (29 kilometers) north of Biscuit Basin. They consulted acoustic and seismic data from the basin’s new monitoring system and determined that the explosion occurred at 2:56 p.m. on April 15, just a few days before roads opened for the spring tourist season.
However, the data does not provide any obvious clues that could be used in the future to develop a warning system.
Ken Sims, a geology professor at the University of Wyoming, conducts long-term studies of where hydrothermal explosions and other ground disturbances might occur in Yellowstone, using ground-penetrating radar and other techniques to identify problem areas.
The information is critical to building roads and bridges in Yellowstone, he said.
“When you build a super-active system like this, you have to pay close attention to what happens,” Sims said.
Developing a detection system takes time and money. The cost of the associated monitoring stations can be around $30,000 each.
But even if we could predict explosions like the recent one in Yellowstone, there is no feasible way to prevent them, Poland said.
“One of the things people ask me every now and then is, ‘How do you stop a volcano from erupting?’ You don’t. You get out of the way,” Poland said. “With this kind of activity, you don’t want to be there when it happens.”
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Hanson reported from Helena, Montana, and Gruver from Cheyenne, Wyoming.