Scientists are probing the depths of the world’s highest geyser

When Steamboat Geyser, the world’s tallest, erupted again in 2018 after decades of relative silence in Yellowstone National Park, it raised some tantalizing scientific questions. Why is it so high? Why is it erupting again now? And what can we learn about it before it becomes quiet again?

The University of Utah has been studying Yellowstone’s geology and seismology and its unique features for decades, so U scientists were ready to take the opportunity to get an unprecedented look at the workings of Steamboat Geyser. Their findings paint a picture of the geyser’s depth, as well as redefine a long-assumed relationship between the geyser and a nearby source. The findings are published in the Journal of Geophysical Research-Solid Earth

“We scientists don’t really know what controls a geyser to erupt regularly, like Old Faithful, or erratic, like Steamboat,” said Fan-Chi Lin, an associate professor in the Department of Geology and Geophysics. “The underground pipeline construction probably checks the eruption characteristics of a geyser. This is the first time we have been able to visualize the pipeline construction of a geyser to more than 100 meters deep.”

Meet Steamboat Geyser

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

“It’s amazing to see a massive steamboat Geyser eruption,” said Jamie Farrell, a research assistant at the University of Utah Seismograph Stations. ‘What I remember most is the sound. You can feel the rumble and it sounds like a jet engine. I already knew that Steamboat was the tallest active geyser in the world, but when I saw it in a major eruption, I was blown away. ‘

Unlike its famous cousin, Steamboat Geyser is anything but loyal. It has had only 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 more eruptions have already occurred in the current phase of geyser activity than in the previous phases.

Close to Steamboat Geyser is a swimming pool called Cistern Spring. Since Cistern Spring deflates when Steamboat erupts, the two functions are believed to be directly linked.

“With our ability to rapidly deploy seismic instruments in a non-intrusive manner, this current era provides the opportunity to better understand the dynamics of Steamboat Geyser and Cistern Spring, which goes a long way towards understanding eruption behavior,” says Farrell.

Give the geyser a CT scan

For several years now, U scientists have been studying the features of Yellowstone National Park, including Old Faithful, using small, portable seismometers. The instruments the size of a football can be used by the dozens where the researchers need a maximum of one month per deployment to get an idea of ​​what is happening underground. Every little movement of the ground, even the periodic swell of crowds on Yellowstone’s boardwalks, is felt and recorded.

And just as doctors can use multiple X-rays to take a CT scan of the interior of a human body, seismologists can use multiple seismometers to record multiple seismic events (in this case, bubbling in the geyser’s superheated water column) to form a kind of image of the background.

In the summers of 2018 and 2019, Farrell and colleagues worked with the National Park Service and placed 50 portable seismometers in an array around Steamboat Geyser. The 2019 bet recorded seven major eruptions, spaced three to eight days apart, each of which provided a wealth of data.

Plumbing the depths

The results showed that the underground channels and crevasses that make up the Steamboat Geyser reach at least 140 meters deep. That’s much deeper than Old Faithful’s plumbing, which is about 80 feet high.

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

“This finding precludes the assumption that the two characteristics are related to something like an open pipe, at least in the top 140 meters,” said Sin-Mei Wu, a recent PhD student working with Lin and Farrell. However, that does not mean that the two functions are completely separate. The fact that the pool drains when Steamboat erupts suggests that they are somehow still connected, but likely through small fractures or pores in the rock that cannot be detected using the seismic signals recorded by the researchers . “Understanding the exact relationship between Steamboat and Cistern will help us model how Cistern might affect Steamboat’s eruption cycles,” added Wu.

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

“We now have a baseline of what eruptive activity looks like for Steamboat,” noted Lin. “When it becomes less active in the future, we can re-deploy our seismic sensors and get a baseline of what idle periods look like. We can then continuously track data coming from real-time seismic stations through Steamboat and assess whether it sees look like one or the other and get a more real-time analysis of when it looks like it’s switching to a more active phase. ”