Yellowstone Caldera Chronicles is a weekly column written by scientists and collaborators of the Yellowstone Volcano Observatory. This week's contribution is from Michael Poland, geophysicist with the U.S. Geological Survey and Scientist-in-Charge of the Yellowstone Volcano Observatory.
Norris Geyser Basin is known for being the hottest and most dynamic of Yellowstone National Park’s thermal areas—and that’s saying something! It is home to Steamboat Geyser, the tallest active geyser on Earth, and it contains an interesting and chaotic mix of acidic and neutral features in terms of chemistry.
Media Sources/Usage: Public Domain. View Media Details Echinus is a rare acidic geyser. Temperature is measured in the outlet channel that carries much of the erupted water. Rapid temperature increases in geyser outlet channels typically reflect increases in flow due to eruptions.
In the Back Basin of Norris Geyser Basin, about 200 meters (660 feet) away from Steamboat Geyser, is Echinus Geyser. The name comes from mineralogist Albert Charles Peale, who visited the geyser in 1878 and thought the rocks around the geyser looked like sea urchins—a type of animal known as an echinoderm.
The geyser pool is about 20 meters (66 feet) across. Paradoxically, the geyser has an acidic chemistry, and it is the largest acidic geyser in the world. That sounds a bit scary, but the acid is not concentrated. Rather, it’s a bit like orange juice or vinegar.
Acid geysers are rare because acidic water can break down the rock that makes up a geyser’s plumbing system. At Echinus Geyser, however, the composition is due to mixing between acidic gases and neutral waters, and the acidity is not sufficient to eat away at the rock. The somewhat unique water chemistry results in interesting formations and compositions, including the red color (from iron, aluminum, and arsenic) that rims the geyser pool and the silica-covered spiny rocks that give the geyser its name.
The boardwalk around Echinus Geyser contains several benches and multiple tiers of platforms. Visitors to the geyser during most of the 21st century might have wondered why there were so many viewing areas, because eruptions are not common. But in the latter half of the 20th century, the geyser was a consistent performer, and visitors could get closer to an eruption there than almost anywhere in the park!
The geyser appears to have been mostly dormant with only occasional eruptions prior to 1948. In the 1970s Echinus Geyser was erupting regularly at 40–80-minute intervals. In the 1980s and 1990s, the eruption durations could be quite extreme, sometimes lasting more than 90 minutes!
Eruptions of Echinus Geyser varied tremendously when the geyser was vigorously active. Some were small while others reached about 23 meters (75 feet). They could be vertical or inclined, occasionally soaking onlookers with warm water, and could be regular enough that the park would sometimes post predictions—the duration of an eruption could often be used to forecast the timing of the subsequent eruption. By the early 2000s, however, eruptions started to wane, and activity became much less common.
In 2010, a temperature monitoring system was established in the outflow channel of Echinus Geyser as a means of tracking any changes. Data from that system recorded 15 sporadic eruptions during October 2010–January 2011. After that time there were a few eruptions here and there until the geyser came alive in 2017.
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