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Yellowstone’s Echinus Geyser Awakens After Five-Year Slumber
Yellowstone National Park announced Monday that the world’s largest acidic geyser, Echinus Geyser, has begun erupting once again after a five-year period of inactivity. Located in the Norris Geyser Basin’s back basin, the geyser, approximately 66 feet wide, is known for the sea urchin-like rocks that surround it, from which it derives its name. Mineralogist Albert Charles Peale first noted this resemblance in 1878.
Echinus Geyser’s unique acidity stems from a blend of acidic gases and neutral waters. While many acidic geysers erode their surrounding rock formations, the acidity at Echinus is not potent enough to cause significant erosion.
The park describes its acidity as akin to “orange juice or vinegar,” rather than a highly concentrated acid. This distinctive water chemistry contributes to the striking red coloration around the geyser pool and the spiny rock formations.
Historically, Echinus was a frequent performer, particularly in the latter half of the 20th century. Viewing platforms and benches allowed visitors unparalleled proximity to its eruptions.
In the 1970s, eruptions occurred every 40 to 80 minutes. By the 1980s and 1990s, eruptions could last up to 90 minutes and propel water as high as 75 feet, occasionally even soaking visitors with warm water in horizontal bursts.
The geyser’s activity began to decline in the early 2000s. A temperature monitoring system installed in its outflow channel in 2010 recorded 15 sporadic eruptions between October 2010 and January 2011.
Activity remained sparse until October 2017, when consistent eruptions occurred for several weeks before abruptly ceasing. Subsequent years saw only a handful of eruptions, indicating a largely inactive state.
Signs of renewed activity emerged in February 2026, with an initial eruption on February 7, followed by additional activity throughout the subsequent week. Regular eruptions, reaching 20-30 feet, commenced every few hours starting February 16. Recent days have shown spikes in activity that typically precede eruptions, although no actual eruptions have been recorded, according to temperature data.
Park officials caution that it is unlikely the geyser will continue erupting into the summer, but acknowledge the unpredictable nature of these geological phenomena.