After grapefruit-sized rocks destroyed a boardwork in eruption, small explosions at Biscuit Basin possible

A recent hydrothermal explosion in Biscuit Basin, Yellowstone National Park, catapulted grapefruit-sized rocks, leading to significant damage to nearby infrastructure. The blast, which occurred just before 10 a.m. on Tuesday, July 23, destroyed a boardwalk and has spurred governmental agencies to warn that small explosions in the area may continue in the coming days to months.

What Happened?

The explosion, associated with the Black Diamond Pool, resulted from water in the shallow hydrothermal system suddenly transitioning to steam, rather than being caused by any volcanic activity. Monitoring services have reported that seismicity, ground deformation, and gas and thermal emissions remain within their normal levels, with no detectable precursors to the event.

The force of the explosion sent steam and debris hundreds of feet into the air, with the largest debris blocks, measuring up to 3 feet wide and weighing hundreds of pounds, were directed towards the northeast. Fortunately, there were no injuries reported during the incident.

Impact on Surrounding Features

The impact of the explosion affected the Black Diamond Pool and Black Opal Pool. While both pools remain, the shape of Black Diamond has changed due to the force of the eruption. Both pools are currently murky thanks to the debris, and unstable ground around their edges has been observed to occasionally slide into the water.

Following the eruption, the water level in the Black Diamond Pool rose over the course of the day, transitioning from minor roiling to occasional bursts of hot water, reaching around 8 feet in height.

What is Happening Now?

As of Wednesday morning, July 24, the water levels in both the Black Diamond Pool and Black Opal Pool had risen to the point of overflowing, sending murky water into the Firehole River. There were no water bursts witnessed from the Black Diamond Pool on Wednesday morning.

Ongoing Hazards

Due to the recent shift in the hydrothermal plumbing system, experts from the United States Geological Survey and Yellowstone National Park warn that small explosions of boiling water from the area may continue over the coming days to months. Agencies will continue to closely monitor conditions, map the debris field, and sample water to assess any changes in the shallow hydrothermal system.

Hydrothermal explosions typically occur in Yellowstone National Park one to a few times per year, but often in the backcountry where they are not immediately detected. However, significant hydrothermal explosions, similar in size to the July 23, 2024 event, occurred back in the 1880s at Excelsior Geyser, in Midway Geyser Basin.

Protection Measures

As a safety precaution, Yellowstone National Park has closed Biscuit Basin for the remainder of the 2024 season. However, the Grand Loop Road remains open to vehicles, and other nearby thermal basins, like Black Sand Basin, remain accessible to the public.

The Yellowstone Volcano Observatory (YVO), tasked with long-term monitoring of volcanic and earthquake activity in the Yellowstone National Park region, continues to diligently monitor the situation.