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The Yellowstone Caldera, located in Yellowstone National Park, is one of the world's most fascinating and potentially dangerous natural wonders. Formed from a series of massive volcanic eruptions, the caldera is essentially a vast volcanic crater, stretching approximately 30 by 45 miles – roughly the size of Tokyo. This geological marvel is the result of three supereruptions over the past 2.1 million years, with the most recent one occurring around 640,000 years ago. Beneath the picturesque landscapes of Yellowstone lies a vast reservoir of magma, which fuels the park's famous geothermal features, including geysers, hot springs and fumaroles.
Yellowstone's geothermal wonders are a stark reminder of the powerful forces simmering beneath our feet. With over 10,000 hydrothermal features, the park's crown jewel is Old Faithful, drawing in the lion's share of the park's four million annual visitors. This region has seen three massive super eruptions in the past 2.1 million years: one 2.1 million years ago, another 1.3 million years ago, and the most recent 640,000 years ago. These numbers suggest an eruption interval of roughly 600,000 to 800,000 years.
In the short term, geothermal activity poses its own risks, as highlighted by recent events in the Biscuit Basin area of the park.
On July 23, 2024, an unexpected explosion rocked Biscuit Basin, leading to the area's temporary closure. The blast caused significant damage to the boardwalk and nearby infrastructure, sparking concerns about visitor safety and the unpredictable nature of Yellowstone's geothermal system. Thankfully, no injuries were reported.
A National Park Service (NPS) press release provided a harrowing account of the hydrothermal explosion. It “sent steam and debris hundreds of feet into the air, destroyed a nearby boardwalk, and ejected grapefruit-sized rocks tens to hundreds of feet from the source. Some blocks closest to the explosion site are about 3 feet (1 meter) wide and weigh hundreds of pounds. The explosion was largely directed to the northeast toward the Firehole River, with the largest blocks of debris falling in that direction. The dark color of the explosion was due to mud and debris mixed with steam and boiling water.”
Biscuit Basin, named for the biscuit-like formations that were once found there, is home to several notable hot springs and geysers, including Sapphire Pool and Jewel Geyser. Tuesday's explosion was likely caused by a sudden release of steam and hot water, a phenomenon that can occur when underground pressure builds up and finds an escape route to the surface. Such events, while rare, are not unprecedented in Yellowstone's history.
Bill Bryson, in his book “A Short History of Nearly Everything,” vividly describes the potential dangers of the Yellowstone supervolcano: “Yellowstone has gone off roughly every 600,000 years, and it is now 640,000 years since the last eruption. On that basis, it is overdue for an explosion of an extravagant kind” (Bryson, p. 185). He further elaborates on the scale of such an event, stating, “The Yellowstone explosion, however, was beyond all imagining. It covered all or parts of nineteen western states, plus parts of Canada and Mexico, in ash up to a depth of three feet” (Bryson, p. 186).
The Yellowstone Caldera is closely monitored by the Yellowstone Volcano Observatory (YVO), a collaborative effort between the United States Geological Survey (USGS), the University of Utah and Yellowstone National Park. The YVO employs a network of seismometers, GPS stations and other instruments to track precursors to an eruption.
Despite the dramatic nature of the recent explosion, experts say there's no immediate threat of a volcanic eruption. Yellowstone's volcanic system is complex and has weathered numerous small-scale disturbances without triggering a major eruption. However, this incident serves as a stark reminder of the caldera's dynamic nature and underscores the importance of ongoing research and monitoring to ensure public safety.
Small explosions of boiling water in Biscuit Basin remain a possibility over the coming months. USGS and NPS geologists will be closely monitoring conditions, mapping the debris field and sampling water to assess any changes in the hydrothermal system in the days to come.
Hydrothermal explosions typically occur in the park one to a few times per year, often in remote areas where they may not be immediately detected.
Smaller hydrothermal explosions have happened before, like in 1989 at Porkchop Geyser in Norris Geyser Basin and in 2009 at Wall Pool in Biscuit Basin. Significant explosions, likely similar in size to Tuesday's, occurred in the 1880s at Excelsior Geyser in Midway Geyser Basin.
For visitor safety, Yellowstone National Park has closed Biscuit Basin for the remainder of the 2024 season. Grand Loop Road remains open to vehicles and other nearby thermal basins, like Black Sand Basin, are open. For more information about visitor access, visit the National Park Service's website.
While the recent explosion in Biscuit Basin has temporarily restricted access to some areas, Yellowstone continues to welcome tens of thousands of visitors each day, who come to marvel at its natural beauty and geological wonders.
The Yellowstone Caldera, with its unique blend of beauty and volatility, remains a testament to the awe-inspiring power of nature.
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