Bold claim: The world’s largest acidic geyser has awakened in Yellowstone after more than five years of silence. But here’s where the story gets even more intriguing...
A few lines about the core facts first: Echinus Geyser, situated in Yellowstone’s Norris Geyser Basin back area, has reactivated after a long dormancy. It sits roughly 66 feet wide and is encircled by sea-urchin-like rocks. The name Echinus comes from those distinctive formations, a nickname given by mineralogist Albert Charles Peale during his 1878 visit.
What makes Echinus special is its acidity. The geyser’s acidic environment results from a blend of acidic gases and relatively neutral water. Unlike many acidic springs that slowly wear away the rock that makes up a geyser, the acidity here isn’t strong enough to erode the surrounding stone. The acidity is not concentrated; park officials describe it as something akin to orange juice or vinegar. This unique chemistry contributes to striking visual phenomena, including the red coloration around the pool and the spiny rock rim.
Historically, Echinus was highly active in the latter half of the 20th century. Observers could get exceptionally close thanks to viewing platforms and benches that the park built specifically for this site. In the 1970s, eruptions occurred roughly every 40 to 80 minutes. The 1980s and 1990s saw longer eruptions—up to about 90 minutes—reaching heights of up to 75 feet, and some flows even shot horizontally, soaking nearby visitors.
Activity waned in the early 2000s. A temperature monitoring system installed along the geyser’s outflow channel in 2010 helped track changes. Between October 2010 and January 2011, the system logged 15 sporadic eruptions. After a quiet period, eruptions briefly reappeared in October 2017, but then the activity dwindled again for years.
In February 2026, signs of renewed activity emerged. Echinus erupted on February 7 and continued intermittently throughout the following week, with regular 20–30 foot eruptions occurring every few hours starting around February 16.
In more recent days, the geyser has shown spikes in activity that typically precede eruptions, as indicated by a temperature graph. While current park assessments suggest it is unlikely for Echinus to maintain year-round eruptions, scientists can’t precisely forecast its behavior in the near term.
If you’re curious for more, you can explore Yellowstone’s official resources on Echinus Geyser and other geothermal features, which provide ongoing updates and context about how these extraordinary natural systems behave over time.
Discussion prompt: Do you think such dramatic geothermal awakenings should influence how we plan park safety messaging and visitor access, or is the best response simply to watch and learn from whatever nature presents next?
