This rhythmic beating of Yellowstone’s hot springs makes it a geothermometer – Ars Technica

It is famous for Yellowstone National Park Old Believers, a geyser with periodic and somewhat predictable volcanic eruptions that delight visiting tourists. But it is also home to many others geothermal features Likes Double pool, a pair of hot springs connected to a small neck with the geothermal equivalent of a pulse. The pool “hits” every 20-30 minutes, causing the water to shake and the floor to vibrate. Researchers at the University of Utah measured those massive cycles with seismometers to learn more about how they change over time. Among other findings, they discovered that the periods of silence between strikes correlate with the amount of heat flowing into the pool, according to new leaf Published in Geophysical Research Letters.

“We knew Doublet Pool hits every 20-30 minutes,” said co-author Fan Zhi Lin, a geophysicist at the University of Utah. “But there wasn’t a lot of previous knowledge about what controls variance. In fact, I don’t think a lot of people actually realize that the mega-interval varies. People pay more attention to heaters.”

The developing hydrothermal system in Yellowstone is the result of the interaction of shallow groundwater with heat from a hot magma chamber. The system features about 10,000 geothermal features, including steam vents (fumaroles), clay pots, and limestone terraces (white, chalky rock), as well as geysers and hot springs.

In the case of geysers, the high pressures prevent the deep water from boiling. But as the hot water rises, the pressure drops and bubbles of steam form, expanding until they are too large to pass through the geyser’s narrow channel near the surface. Eventually the bubbles reach a critical threshold and the heater begins to flow. The pressure drops sharply and the water boils, creating large amounts of steam that forces a gush of hot water out of the vent in one of those volcanic eruptions that are so satisfying. Then the cycle begins again.

By contrast, most hot springs maintain a fairly stable hydrodynamic balance. The superheated water cools as it reaches the surface, sinks, and is replaced by hotter water from below, so the water never reaches the required temperature needed for an eruption to occur. However, some hot springs, like Doublet Pool and Iodine Pool in New Zealand, have those fuzzy periodic outcrops that resemble a periodic geyser eruption pattern: When bubbles of hot water vapor reach the cooler upper parts of the channel, they suddenly collapse with a kick. .

By studying Doublet Pool, Lin and his authors hoped to learn more about the dynamic hydrothermal processes in Yellowstone. They specifically wanted to explore what controls the differences that occur during hot spring eruptions or hot spring beating cycles, so they decided to focus on measuring periods of silence between strikes. From the fall of 2015 through November 2021, they ran several sampling experiments with geophones set up near Doublet Pool. They also collected temperature data in November 2021 and pressure data to monitor changes in water levels for four days in April 2022.

flexible et al. She found that periods of silence varied not only year by year but also from hour to hour or day to day. For example, the interval was about 30 minutes in November 2016 but only 13 minutes in September 2018, and it increased to about 20 minutes by November 2021. That happens exactly on September 15, 2018, in the vicinity ear spring It erupted for the first time since 1957, and after that, Doublet Pool water boiled. According to the authors, all that heat and pressure decreased by 2021, so Doublet Pool’s silence period began to return to its normal 30-minute duration.

For daily and hourly differences, the authors suggest there could be a correlation with wind speed. Higher wind speeds appear to be associated with longer periods of silence, which means that the wind removes thermal energy from the water in some way, like blowing on a hot cup of coffee. “Currently, we treat the pool as one complete system, which means that the energy taken up from the surface makes it difficult for the system to accumulate enough energy to hit it,” Lynn said. “One possibility is that the pool is convectively transported, 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 the amount of heat needed to cause strikes in Doublet Pool: about 3 to 7 megawatts of power, equivalent to the power output of 100 home furnaces. This, in turn, enables them to use the period of silence as a thermometer, to gauge how much heat is coming into the pond. (More heat means shorter periods.)

DOI: Geophysical Research Letters, 2023. 10.1029 / 2022GL101175 (about DOIs).

Listing image by WikiBunny11 / CC BY-SA 4.0.0