Scientists explore the depths of the world’s tallest geyser

When the world’s tallest Steamboat Geyser began to erupt again in Yellowstone National Park in 2018 after decades of relative silence, it raised some tantalizing scientific questions. Why is he so tall? Why is it erupting again now? And what can we learn from it before it becomes silent again?

The University of Utah has been studying the geology and seismology of Yellowstone and its unique features for decades, so scientists in Utah were ready to seize the opportunity to have an unprecedented look at how Steamboat Geyser. Their findings provide a picture of the depth of the geyser as well as a redefinition of a long-believed relationship between the geyser and a nearby source. The results are published in the Geophysical Research Journal – Solid Earth.

“We scientists don’t really know what keeps a geyser from erupting regularly, like Old Faithful, versus irregularly, like Steamboat,” says Fan-Chi Lin, associate professor in the Department of Geology and Geophysics . “The underground plumbing structure probably controls the eruption characteristics of a geyser. This is the first time we have been able to imagine the plumbing structure of a geyser deeper than 325 feet (100 m) deep. . “

Meet Steamboat Geyser

If you are asked to name a Yellowstone geyser and “Old Faithful” is the only one that comes to mind, then you are late for an introduction to Steamboat. Recorded eruption heights reach up to 110 meters, enough to splash the top of the Statue of Liberty.

“Watching a major eruption from the Steamboat Geyser is pretty amazing,” says Jamie Farrell, assistant research professor at the University of Utah Seismograph Stations. “What I remember most is the sound. You can feel the rumble and it looks like a jet engine. I already knew that Steamboat was the tallest active geyser in the world, but seeing it erupting majorly. blew me away. “

Unlike its famous cousin, Steamboat Geyser is anything but faithful. There have only been three periods of sustained activity in recorded history – one in the 1960s, one in the 1980s, and one that began in 2018 and continues today. But the current phase of geyser activity has already seen more eruptions than either of the previous phases.

Near Steamboat Geyser is a swimming pool called Cistern Spring. Since Cistern Spring drains when Steamboat erupts, it is assumed that the two functions are directly connected.

“With our ability to rapidly deploy seismic instruments in a non-intrusive manner, this current period provides the opportunity to better understand the dynamics of Steamboat Geyser and Cistern Spring, which greatly helps us understand eruptive behavior,” says Farrell.

Give the geyser a scanner

For several years now, U scientists have been studying features of Yellowstone National Park, including Old Faithful, using small portable seismometers. The football-sized instruments can be deployed by the dozen anywhere researchers need them for up to a month per deployment to get a picture of what’s going on under the ground. Every slight little movement of the ground, even the periodic swells of crowds on the sidewalks of Yellowstone, is felt and recorded.

And just as doctors can use multiple x-rays to create a scanner of the interior of a human body, seismologists can use multiple seismometers recording multiple seismic events (in this case, bubbling in the geyser’s superheated water column). to build a kind of image of the basement.

During the summers of 2018 and 2019, Farrell and his colleagues worked with the National Park Service and placed 50 portable seismometers in a network around Steamboat Geyser. The 2019 deployment recorded seven major eruptions, with a range of eruption periods spaced three to eight days apart, each providing a wealth of data.

Plumbing in the depths

The results showed that the underground channels and cracks that make up Steamboat Geyser extend for at least 450 feet (140 m). It’s much deeper than Old Faithful’s plumbing, which is around 80 meters.

The results does not have however show a direct connection between Steamboat Geyser and Cistern Spring.

“This discovery rules out the hypothesis that the two elements are related to something like an open pipe, at least in the top 140 meters,” says Sin-Mei Wu, a recently graduated doctoral student working with Lin and Farrell. That’s not to say that the two features are entirely separate, however. The fact that the pool drains when Steamboat erupts suggests that they are still connected somehow, but likely through small fractures or pores in the rock that are not detectable at the using seismic signals recorded by researchers. “Understanding the exact relationship between Steamboat and Cistern will help us model how the cistern might affect Steamboat eruption cycles,” Wu added.

Will scientists eventually be able to predict when the geyser will erupt? Maybe, Wu says, with a better understanding of the hydrothermal tremor and a long-term monitoring system. But, in the meantime, says Wu, this study is really just the beginning of understanding how Steamboat Geyser works.

“We now have a basis of what the eruptive activity looks like for Steamboat,” Lin pointed out. “When it becomes less active in the future, we can redeploy our seismic sensors and get a baseline of what non-active periods look like. We can then continuously monitor the data coming from the seismic stations in real time by Steamboat and assess if they look like one or the other and get a more real time analysis of when it seems to move to a more active phase. . ”