Old Faithful

Bob Smith, distinguished professor of geology and geophysics at the University of Utah, will speak at 6 p.m. Tuesday at Teton County Library. He will outline his newest research on volcanism in Yellowstone, mapping the underground hydrothermal reservoirs that fuel the Old Faithful and Steamboat geysers.

The Geologists of Jackson Hole’s next guest needs no introduction.

Bob Smith, distinguished professor of geology and geophysics at the University of Utah and a veteran Yellowstone researcher, will speak Tuesday at the Teton County Library about his latest research on the underground systems that fuel Yellowstone’s most famous geysers. The talk is set to start at 6 p.m. in the Ordway Auditorium.

Smith has been studying Yellowstone for 63 years, and this new research represents the final piece in putting together the puzzle of Yellowstone’s volcanic systems.

“We’ve basically unravelled the whole plumbing system of Yellowstone,” Smith said.

Over the years Smith, along with other scientists, has examined volcanic activity in Yellowstone from beneath-the-ground up. Yellowstone’s volcanism originates 1,800 miles below the surface of the Earth, where the mantle meets the core. The research then follows a trail of molten rock upward, where eventually the rock directs magma into two reservoirs about 2 to 3 miles beneath Old Faithful.

In the last few years Smith has focused his research on learning the details of the mile just beneath the surface: The last piece of the geyser’s plumbing.

Before Smith’s recent studies not much was known about the underground geology of Old Faithful. Over the last few years Smith and his team have been able to create a complete image of the crustal system and hydrothermal reservoir that fuel the geyser, providing a better understanding of the local conditions that affect it.

Old Faithful sits at the edge of a large hydrothermal reservoir composed of highly fractured rock, hot water and steam. The geyser itself is like a release valve, Smith said, so the magma reservoir farther beneath the surface heats the groundwater and eventually boils it and causes an eruption.

Scientists can use data from large earthquakes to map features deep beneath the surface, but new tools allowed the team to measure the small everyday tremors around the reservoir, which was necessary to accurately map the geology just below the surface. Through seismographic monitoring they learned the eruptions at Old Faithful do not correspond with strong seismic signals but instead with activity about 95 minutes before each eruption.

After Old Faithful, Smith and the team moved on to Steamboat Geyser, placing dozens of similar seismographs to map its underground geology. At the library talk Smith will discuss the initial conclusions from that data.

Smith attributes the recent increase in Steamboat eruptions to record precipitation in Yellowstone, leading to higher groundwater levels. During the spring and summer, as the groundwater level decreases, it reduces the pressure on the hydrothermal reservoir that fuels Steamboat, allowing more water to escape. Smith likens the system to a steam kettle.

“If you reduce the pressure on the lip of the steam kettle, water is going to come out easier and faster,” he said. “I think that’s what’s happening at Steamboat — the water pressure goes down, allowing a higher volume of water to escape in shorter intervals.”

Through his past experience and newest findings, Smith’s presentation will map Yellowstone’s volcanism from the core of the Earth to the shallow reservoirs that fuel its most-visited landmarks. 

Contact Frederica Kolwey via 732-7062 or entertainment@jhnewsandguide.com.

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