Sudden Eruption Shocks Tourists
On Tuesday, July 23, at approximately 10:19 a.m., a sudden hydrothermal explosion occurred near Sapphire Pool in Biscuit Basin, Yellowstone National Park. The explosion sent visitors scrambling for safety as steam, rocks, and debris were ejected into the air. The event, which temporarily closed the Biscuit Basin area, including its parking lot and boardwalks, has drawn significant attention both online and from park authorities.

Eyewitness Accounts and Immediate Impact
Visitors at the scene described the eruption as terrifying. Vlada March, a tourist who captured the event on video, shared her harrowing experience on social media. In her video, she can be heard urging people to run as the black cloud of debris rose into the sky. “It just exploded and became like a black cloud that covered the sun,” March recounted. The video quickly went viral, with thousands of views and shares.
Visitors at the scene described the eruption as terrifying. Vlada March, a tourist who captured the event on video, shared her harrowing experience on social media. In her video, she can be heard urging people to run as the black cloud of debris rose into the sky. “It just exploded and became like a black cloud that covered the sun,” March recounted. The video quickly went viral, with thousands of views and shares.
Despite the dramatic nature of the explosion, no injuries were reported. However, the boardwalks in Biscuit Basin sustained significant damage from falling rocks and debris. March noted that her mother was hit by some debris but was otherwise unharmed.
Understanding Hydrothermal Explosions
Hydrothermal explosions in Yellowstone are not unprecedented. Mike Poland, a research geophysicist and scientist-in-charge at the Yellowstone Volcano Observatory, explained that these events occur multiple times a year. “They are episodes of water flashing to steam underground, often triggered by the natural underground plumbing system,” Poland said. He emphasized that such explosions are part of the park’s dynamic geothermal activity and do not indicate any imminent volcanic activity.

In the case of Tuesday’s explosion, there was no associated earthquake, which is sometimes a trigger for these events. Instead, it is believed that the explosion was caused by a clog in the underground passageways, leading to a sudden buildup of pressure and steam.
Historical Context of Hydrothermal Activity
Biscuit Basin, located just north of the famous Old Faithful geyser, has a history of hydrothermal activity. A similar explosion occurred in Biscuit Basin in May 2009, and another notable event took place in 1991. The basin itself is named for the biscuit-like deposits that once surrounded Sapphire Pool, which were blown away during a significant eruption following the 1959 Hebgen Lake earthquake.

Yellowstone National Park is centered on a massive, dormant volcano, and while hydrothermal explosions are relatively common, they are usually small and localized. The largest known hydrothermal explosion crater in Yellowstone, located in the Mary Bay area, measures 1.5 miles across and dates back approximately 13,800 years.
Ongoing Monitoring and Safety Measures
Following the explosion, park staff, along with experts from the US Geological Survey (USGS), have been closely monitoring the area. The Biscuit Basin parking lot and boardwalks will remain closed until they are deemed safe for visitors. In the meantime, the Grand Loop Road remains open, allowing access to other parts of the park.

The USGS has reassured the public that Tuesday’s explosion does not signify any changes in the Yellowstone volcanic system, which remains at normal background levels of activity. “Today’s explosion is a reminder of the unpredictable nature of Yellowstone’s geothermal features,” the agency stated.
The hydrothermal explosion at Biscuit Basin serves as a stark reminder of the power and unpredictability of Yellowstone’s geothermal activity. While such events can be startling, they are part of what makes Yellowstone National Park a unique and dynamic natural wonder. Visitors are always urged to stay on designated trails and boardwalks to ensure their safety while exploring this extraordinary landscape.
For the latest updates on the status of Biscuit Basin and other areas of Yellowstone National Park, visitors are encouraged to check official park communications and the USGS monitoring reports.