The oscillating water surface of Doublet Pool in Yellowstone National Park.Credit: Jamie Farrell/University of Utah
Yellowstone National Park is most famous for Old Faithful, a geyser with fairly predictable periodic eruptions that delight visiting tourists. But it’s also home to many other geothermal features, such as the Doublet Pool, a pair of hot springs connected by a small neck whose geothermal equivalent is a pulse. The pool “throbs” every 20-30 minutes, shaking the water and shaking the ground. Researchers at the University of Utah used seismographs to measure the frequency of these bangs and see how they changed over time. Among other findings, they found that intervals of silence between pounding correlated with the amount of heat flowing into the pool, according to a new paper published in the journal Geophysical Research Letters.
“We knew the doublet pool would hit every 20 to 30 minutes,” says co-author Fan-Chi Lin, a geophysicist at the University of Utah. “But there wasn’t a lot of previous knowledge about what controlled the fluctuations. In fact, I don’t think many people realize that the pounding intervals are different. People should pay more attention to geysers.” pay.”
Yellowstone’s elaborate hydrothermal system is the result of shallow groundwater interacting with heat from hot magma chambers. The system has about 10,000 geothermal features, including steam vents (fumaroles), mud pots, and travertine terraces (chalk-like white rocks), as well as geysers and hot springs.
For geysers, high pressure prevents deep water from boiling. However, as the hot water rises, the pressure drops and steam bubbles form, expanding until they are too large to pass through the geyser’s narrow conduits near the surface. , the geyser begins to overflow. A sudden drop in pressure causes the water to boil, producing a large amount of steam, and hot water is ejected from the spout. He is one of the crowd-pleasing eruptions. Then the cycle starts over.
In contrast, most hot springs maintain a fairly stable hydrodynamic balance. When the superheated water reaches the surface, it cools, sinks, and is replaced by hotter water from below, so the water never reaches the temperature required to initiate an eruption. However, some hot springs, such as New Zealand’s doublet pools and iodine pools, have mysterious periodic eruption patterns that resemble the periodic eruption patterns of geysers. When the heated steam bubble reaches the cold upper part of the conduit, it suddenly collapses. .
By studying the doublet pool, Lin and co-authors hoped to learn more about the dynamic hydrothermal processes in Yellowstone. They specifically wanted to explore what controls the fluctuations that occur during cycles of geyser eruptions and hot spring thumps, so they decided to focus on measuring intervals of silence between thumps. From the fall of 2015 to his November 2021, they set up a geophone near the doublet pool and conducted several sampling experiments. Also in November 2021 he collected temperature data and in April 2022 he collected pressure data to monitor water level changes over a four-day period.
Rin othersIt turns out that the interval between silences varies not only from year to year, but also from hour to hour, or even day to day. For example, this interval he was about 30 minutes in November 2016, only 13 minutes in September 2018, and increased to about 20 minutes by November 2021. On September 15, 2018, a nearby earspring erupted for the first time since his 1957. , and then the water in the doublet pool boiled. By 2021, according to the author, as the heat and pressure had all subsided, doublet pool silence intervals began to return to his normal 30-minute intervals.
The authors suggest that daily and hourly variations may be correlated with wind speed. Higher wind speeds appear to correlate with longer silence intervals. This means that the wind is somehow removing heat energy from the water, similar to how it blows hot coffee. “Currently, we treat the pool as a whole system, which means that when the surface is deprived of energy, it becomes difficult for the system to accumulate enough energy,” he said. I’m here. “One possibility is that the pool is actively convecting, so cooling near the surface could affect the bottom of the pool on a relatively short timescale.
The authors were also able to calculate the heating rate and amount of heat required to pound in the doublet pool. This is about 3-7 megawatts of energy, equivalent to the energy output of 100 domestic stoves. This allows you to use the silence interval as a thermometer to measure the amount of heat entering the pool. (More heat equals shorter intervals.)
DOI: Geophysical Research Letters, 2023. 10.1029/2022GL101175 (About DOI).
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