World’s Largest Acidic Geyser Awakens in Yellowstone After Six-Year Dormancy
London, 4 March 2026 – Geologists and park visitors at Yellowstone National Park have witnessed a rare natural spectacle as Echinus Geyser, the world’s largest acidic geyser, returned to activity following a prolonged period of dormancy. Located in the Norris Geyser Basin, the geyser had remained largely silent since 2020. However, recent observations confirmed a significant burst of activity beginning in mid-February, marking its first major eruptive phase in six years.
A Rare Hydrothermal Event
Echinus Geyser is unique among the world’s hydrothermal features due to its highly acidic composition. While most geysers are alkaline or neutral, Echinus possesses a pH level ranging between 3.3 and 3.6, making its waters nearly as acidic as vinegar. This acidity is caused by the mixing of neutral groundwater with acidic gases rising from the underlying magmatic system.
According to the Yellowstone Volcano Observatory (YVO), the current cycle of activity intensified on 16 February 2026. During this peak, eruptions were recorded at intervals of every two to five hours. By the end of February, the geyser had erupted approximately 40 times. While historical eruptions in the 1970s were known to reach significant heights and last up to 90 minutes, these recent displays have been more modest, typically lasting two to three minutes and reaching heights of 20 to 30 feet.
Key Facts: Echinus Geyser
The following table outlines the technical specifications and historical data regarding this rare geological feature as confirmed by the U.S. Geological Survey and National Park Service.
| Category | Details |
|---|---|
| Location | Norris Geyser Basin, Yellowstone National Park |
| Classification | Largest acidic geyser in the world |
| Acidity (pH) | 3.3 to 3.6 (Comparable to vinegar) |
| Pool Diameter | Approximately 20 metres (66 feet) |
| Water Temperature | 80.3 °C (176.5 °F) |
| Last Active Period | 2020 (Prior to February 2026) |
| Recent Eruption Height | 20 to 30 feet |
Frequently Asked Questions
Is the acidic water dangerous to visitors?
While the water is acidic enough to be scientifically notable, it is not concentrated enough to “eat through” materials instantly. However, the primary danger to visitors remains the extreme temperature of the water (80.3 °C), which can cause severe burns. Visitors must remain on designated boardwalks at all times.
Why is it called “Echinus”?
The geyser is named after the Latin word for sea urchin (Echinus). This refers to the spiky, iron-rich silica formations and reddish rocks that surround the geyser’s rim, which resemble the spines of the marine creature.
Will the eruptions continue through the summer?
The U.S. Geological Survey has noted that the geyser’s activity is notoriously unpredictable. While it has been “putting on a show” recently, experts warn that the comeback may be brief, and it is unknown whether the current eruptive cycle will persist into the 2026 summer season.