According to the USGS, Yellowstone National Park’s Echinus Geyser, long dormant and often forgotten by casual visitors, has come back to life in early 2026 after years of near-total inactivity.
Located in the Back Basin of Norris Geyser Basin roughly 200 meters from the famous Steamboat Geyser, Echinus holds the title of the largest acidic geyser in the world. Its pool chemistry, driven by a mix of acidic gases and neutral waters, gives the surrounding rocks a striking red appearance, which is how the geyser earned its name from mineralogist Albert Charles Peale who visited in 1878 and likened the formations to sea urchins.
The geyser was a reliable crowd-pleaser for much of the latter 20th century, erupting at predictable intervals and occasionally soaking onlookers with warm water. Eruptions reached heights of up to 75 feet and lasted as long as 90 minutes during its peak years. Activity began tapering off in the early 2000s, and after a brief revival in late 2017, the geyser fell quiet again with only isolated eruptions recorded in 2018, 2019, and 2020.
In early February of this year, temperature sensors in the geyser’s outflow channel began detecting renewed surges. The first confirmed eruption since December 2020 occurred on February 7th. By February 16th, eruptions were occurring every two to five hours, reaching heights of around 20 to 33 feet, and lasting two to three minutes each.
The U.S. Geological Survey’s Yellowstone Volcano Observatory is monitoring the activity in real time. Temperature spikes reaching around 70 degrees Celsius in the outflow channel indicate active eruptions, while lower spikes signal pool surges.
It’s unclear whether this renewed activity will persist into the summer at the world’s largest acidic geyser. Based on past behavior, it may go quiet again before crowds arrive. But for now Echinus is putting on quite the show.
