For scientists working to understand why some geysers erupt with relative regularity and others do not, Yellowstone National Park provides a valuable testbed. Researchers at the University of Utah have been keeping a close eye on these famous streams of airborne water and steam, and have now managed to image the plumbing system of the tallest one in the world. These insights, the team says, could lay the foundation for more accurate monitoring systems that predict when exactly these powerful geysers may be moving to more active phases.
The new research stems from decades of observing the geological activity of Yellowstone National Park by scientists at the University of Utah, who were offered a unique opportunity with the recent and ongoing eruption of Steamboat, the world's tallest geyser, which hits heights of 360 ft (110 m). This follows only two other periods of Steamboat activity in recorded history, in the 1960s and 1980s, a pattern in stark contrast to the park's Old Faithful geyser, which erupts around 20 times every day.
“We scientists don’t really know what controls a geyser from erupting regularly, like Old Faithful, versus irregularly, like Steamboat,” says study author Fan-Chi Lin. “The subsurface plumbing structure likely controls the eruption characteristics for a geyser. This is the first time we were able to image a geyser’s plumbing structure down to more than 325 feet (100 m) deep.”
The scientists were able to form these images of Steamboat's subsurface structures using football-sized seismometers, 50 of which were placed on the ground around the geyser to record seismic activity across 2018 and 2019. This included seven major eruptions and lulls in between, with the events used to compile an image of the structures beneath the surface in a process likened to using multiple X-rays to create a CT scan of the body's interior.
This showed that the plumbing for the Steamboat geyser extends to depths of at least 450 ft (140 m), and revealed new insights between these channels and fissures and the nearby Cistern Spring. Because this body of water drains when Steamboat erupts, it had been thought that there was a direct underground connection between the two, though the images show that this isn't really the case.
“This finding rules out the assumption that the two features are connected with something like an open pipe, at least in the upper 140 meters (460 ft),” says Sin-Mei Wu.
What's more likely, is that the two are connected but only via small pores or fractures in the rock that weren't picked up by the team's methodology. A better understanding of the relationship between the spring and the geyser could help the team model how Cistern can shape eruption cycles, as will longer-term monitoring of seismic activity, particularly as Steamboat enters quieter phases.
“We now have a baseline of what eruptive activity looks like for Steamboat,” Lin says. “When it becomes less active in the future, we can re-deploy our seismic sensors and get a baseline of what non-active periods look like. We then can continuously monitor data coming from real-time seismic stations by Steamboat and assess whether it looks like one or the other and get a more real-time analysis of when it looks like it is switching to a more active phase.”
The research was published in the Journal of Geophysical Research.
Source: University of Utah
