A new study has determined that the US Yellowstone National Park’s Steamboat Geyser has been suffering from decades-long dry spells brought on by a history of droughts. With global temperatures on the rise, the American West is projected to become drier. Sustained drought in this region could slow down, and possibly halt, Yellowstone National Park’s famous geyser eruptions, the researchers say.
“Even small changes in precipitation could affect the interval between eruptions,” explained Shaul Hurwitz, a hydrologist at the US Geological Survey (USGS) who led the study.
Geysers need very specific conditions to form, including a water source, heat supply and the right geologic plumbing. Environmental conditions such as drought can tip that balance and cause geysers to go dormant. Steamboat, the world’s tallest active geyser, can spray water up to about 115m (377ft) into the air for as long as 90 minutes at a time, with eruption intervals ranging from just three days to 50 years.
When the geyser erupts, heated water spray coats nearby trees in silica, a mineral that can prevent decomposition. This silica mist slowly smothers the trees, eventually killing them while preserving the wood’s structure. As a result, dead trees surrounding the geyser can be preserved for centuries longer than usual, making them a useful tool for studying the geyser’s history. The new study aims to reconstruct its past periods of inactivity and determine what caused the changes in the geyser’s activity over the centuries.
Lodgepole pines make up nearly all of Yellowstone’s forests. However, they have an average lifespan of only 150 to 200 years. Hurwitz and his team took advantage of this preservation process and collected silicate wood samples from within 14m (46ft) of the geyser vent. Through radiocarbon dating they found that the tree samples clustered around three time periods: the late 15th century, mid-17th century and late 18th century.
Hurwitz and his team matched the three periods of tree growth around the geyser to regional climate records and found that droughts occurred during the same time that the trees grew. These environmental conditions most likely reduced the local water supply, preventing Steamboat from erupting and allowing the trees to grow – but the geyser never remained dormant for long.
“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,” Hurwitz said. “So there wasn’t an extended period of many decades or centuries with continuous growth.”
But with global temperatures on the rise, extended drought in America’s West could further diminish Yellowstone’s geyser activity.
“As we’re headed toward what’s predicted to be a warmer and drier climate 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 said.
