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Yellowstone’s Steamboat Geyser battled with droughts for centuries

Yellowstone’s famous Steamboat Geyser is the world’s tallest active geyser which can spray water up to 115 meters (377 feet) in the air for periods as long as 90 minutes. A recent study led by the United States Geological Survey (USGS) has found that Steamboat Geyser has experienced decades-long dry spells caused by recurrent droughts during its history. 

Since droughts are now becoming more frequent due to climate change, this geyser’s eruptions could slow down, and even halt completely in the future.

“Even small changes in precipitation could affect the interval between eruptions,” said study lead author Shaul Hurwitz, a hydrologist at USGS. “So more water means more frequent eruptions, while less water means less frequent eruptions.”

To form and erupt, geysers need very specific conditions, including a water source, sufficient heat supply, and the right geological “plumbing.” Environmental extremes such as droughts can change that balance, and cause geysers to become dormant. 

Steamboat is highly unpredictable 

Unlike Yellowstone’s Old Faithful Geyser, which erupts on a predictable schedule, Steamboat’s activity is highly unpredictable, with eruption intervals varying from just three days to half a century. 

When this geyser erupts, its heated water spray covers nearby trees in silica, a mineral which protects against bacteria and fungi and can prevent tree decomposition. As a result, these trees can be preserved for much longer than usual – sometimes even a few centuries – making them a useful tool for investigating the geyser’s history. 

“In Yellowstone, you rarely find any wood, even dead wood, that’s more than 300 years old because the fungi and other bacteria decompose it. The silica essentially protects the tree from the fungi. For us, this is an advantage because if they weren’t silicified we wouldn’t have any trees to date,” Hurwitz explained.

Focus of the study

Yellowstone’s forests consist almost entirely of lodgepole pines, which have an average lifespan of only 150 to 200 years. However, the researchers took advantage of the preservation process caused by eruptions and collected silicate wood samples from within 14 meters (46 feet) of the geyser vent. 

By using radiocarbon dating, they discovered that the tree samples belonged to three time periods – the late 15th century, mid-17th century, and late 18th century.

“Water that is erupting from the geyser is silica-rich, and when silica precipitates it clogs pathways that allow the trees to respire, photosynthesize and grow. For us, this indicates that when trees grow right near the mound there are no eruptions,” Hurwitz said.

What the researchers learned 

By matching the three main periods of tree growth around the geyser to regional climate records, the experts found that droughts occurred during the same time that the trees grew, reducing the local water supply and preventing the geyser from erupting. However, the analysis revealed that Steamboat did not remain dormant for extended periods of time. 

“In the case of Steamboat, we did not find any tree remnant of silicified wood that had more than 10 or 20 annual rings, which suggests to us that trees never grew big around that area. So, there wasn’t an extended period of many decades or centuries with continuous growth,” Hurwitz explained.

Yet, with global temperatures currently on the rise due to climate change, extended periods of droughts in the American West could decrease Steamboat’s activity even further. Even geysers such as the Old Faithful could soon become less “faithful” to their eruption schedule as their water supplies diminish.

“As we’re headed toward what’s predicted to be a warmer and drier climate in the 21st century, we might expect to see the geysers go to totally different behavior in terms of the interval between their eruptions — erupting less frequently, and some of them might even go extinct,” Hurwitz concluded.

The study is published in the journal Geochemistry, Geophysics, Geosystems.

By Andrei Ionescu, Staff Writer

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