The Biscuit Basin Explosion

The world’s first national park – Yellowstone – contains over half of Earth’s geysers. Powering this incredible fact is the Yellowstone Caldera, an underground supervolcano. Though currently dormant in terms of overground eruption, the system isn’t extinct and still heats the region, creating Old Faithful and the other gushers inside the park.

Worrywarts across the nation and globe find consternation in the lurking hotspot beneath Yellowstone. In some ways, they are justified; this supervolcano’s past activity tops the Volcanic Activity Index scale at 8 out of a possible 8. If the Yellowstone Caldera blew, the worldwide climate would be disrupted for decades. However, the chances of an incident remain infinitesimally low and no evidence suggests the system is progressing toward a problem. We can live content in the knowledge that the explosions at Yellowstone will be relatively minor, as the geysers put on daily shows for tourists.

Visitors in July 2024, however, might have a problem with the term “relatively minor.” A group of humans discovered one doesn’t necessarily need lava or ash to make things jump at Yellowstone!

Yellowstone’s geyser activity can be divided into nine main basins. The largest is the Upper Geyser Basin, which includes Old Faithful and more than 400 other geysers. This large region includes some subsections also termed basins, one of which is the Biscuit Basin. The name comes from deposits that formed around Sapphire Pool until they were destroyed during an eruption in 1959.

We tend to think geysers look like Old Faithful, cones that rise from the ground. Sometimes, though, they present as mere holes or lurk below pools. Many spots in Yellowstone look just like Black Opal Pool, pictured above, steaming lakes that oversee hidden hydrothermal activity.

A few of the most famous geysers erupt in regular or semi-regular patterns; others spew more erratically, though fairly often. Every once in a while, though, fireworks can transpire from spots that seem innocuous.

A boardwalk allows humans to view Black Opal Pool and another pool, Black Diamond, inside Biscuit Basin. On 23 July, the people on the trail witnessed this incredible happening:

This explosion was not volcanic in origin but hydrothermal. How can water cause such a brouhaha?

According to the United States Geological Survey:

“Hydrothermal explosions occur where shallow interconnected reservoirs of fluids with temperatures at or near the boiling point underlie thermal fields. These fluids can rapidly transition to steam if the pressure suddenly drops. Since vapor molecules take up much more space than liquid molecules, the transition to steam results in significant expansion and blows apart surrounding rocks and ejects debris.”

The dark portions of the explosion are a mix of mud and debris. The National Park Service estimates particles were ejected hundreds of feet in the air. Boulders three feet wide, weighing hundreds of pounds, emerged from beneath the ground. Grapefruit-sized rocks were found hundreds of feet away.

Despite the proximity to the event, incredibly, the only thing injured was the boardwalk, which was obliterated near Black Diamond Pool:

As massive as this blast was, it was tame by the standards of Yellowstone, even just confined to hydrothermal explosions.

Though rare, these types of bursts can leave craters over a mile wide. As explained by the USGS in the video above, the largest known hydrothermal explosion transpired in Yellowstone at Mary Bay, etching a 1.5-mile hole in the planet.

Many people rank Yellowstone near the top of the natural beauty rankings. Its geysers and chromatic pools can uniquely dazzle visitors. The park is another fantastic example, however, of the tremendous power of the planet. The most beautiful things can carry the power of destruction.

It wasn’t the supervolcano, but the Biscuit Basin explosion might have seemed like the end of the world for the boardwalk’s sightseers. Awe-inducing from afar. No thank you, up close!