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Hot road

Beryl Spring is a hydrothermal area in some restrictive topography. The road from Norris Geyser Basin to Madison Junction follows the Gibbon River through a tight valley. With not much of a choice, the road threads between the river and Beryl Spring over some hot ground. It takes a feat of engineering to keep the road drivable through this area, and sometimes nature has the final say, as in 1942, when this National Park Service photo was taken. Don't fret, the road is now passable by auto and bison.

Yellowstone Caldera Chronicles is a weekly column written by scientists and collaborators of the Yellowstone Volcano Observatory. This week's contribution is from Behnaz Hosseini, geoscientist, and Jefferson Hungerford, park geologist, at the Yellowstone Center for Resources in Yellowstone National Park.

When it comes to building and maintaining infrastructure in Yellowstone National Park, the dynamic character of the environment often requires creative thinking and adaptability. Like long-term monitoring equipment and the elements, park infrastructure is in a running battle with the constantly changing hydrothermal system and geological landscape. However, with enough data and foresight, Yellowstone's geology team and maintenance crews can make informed decisions on where to lay roads, boardwalks, and other facilities to make these structures as lasting, useful and safe as possible for visitors.

Charred boardwalk

A section of the Porcelain Basin Loop boardwalk in the Norris Geyser Basin was removed in 2018 because the ground below sections of the boardwalk became too hot and made charcoal of the wood footings that support the structure. Luckily enough in this case, the boardwalk was shifted about 3 feet to avoid the new hot ground. 

The roadways and boardwalks that lead visitors to Old Faithful, Grand Prismatic Spring, and other iconic hydrothermal features wind through breathtaking yet hazardous terrain. In many hydrothermal areas visitors stand on boardwalks elevated only inches above and feet away from boiling springs and erupting geysers. However, the same hot ground surrounding a hot spring may be tens of degrees cooler just underneath the boardwalk. For example, temperatures exceeding 40 °C (104 °F) were measured at one inch depth in the ground just 2 feet south of the new feature on Geyser Hill (near Old Faithful); only a few feet away underneath the boardwalk, temperatures dropped to an unremarkable 3 °C (37 °F). The placement of the boardwalk over colder ground is not coincidental — Yellowstone's geology team works closely with trail and boardwalk crews to "map the heat" in proposed trail and boardwalk construction areas.

Thermal infrared cameras are as essential to safety and planning as they are to monitoring Yellowstone's hydrothermal system over time. The Geology Team uses infrared remotely sensed imagery to map potential paths for new roadways through hydrothermal areas. We also perform ground based mapping to augment the information gleaned from the IR imagery. Sometimes there is no cool passage through a hydrothermal area, and our road construction team puts foam insulation and other materials at the base of a road to keep the surface in a cool, drivable condition. The road past Beryl Spring is a good example.

Now, we don't often talk about toilets in Yellowstone Caldera Chronicles, but let's break some new ground. Yellowstone sees more than 4 million visitors a year and when nature calls, nature calls — even when you're in a hydrothermal area. In the park, engineers install vault toilets in areas that are not serviced with running water, such as Fountain Paint Pots and Mud Volcano. First, park geologists and engineers must bore holes to depths beyond the base of the vault toilet to locate any warm areas (greater than 25 °C) in the ground. Sometimes, these warm zones are not identified until a pit is excavated; in that case, the search for a site amenable to toilets must continue.

Roads, boardwalks, and vault toilets pose just a few of the challenges to introducing millions of park guests to a volcanic system and the wonders of Yellowstone each year. These challenges are well worth the effort, though. The next time you visit Yellowstone and walk on the boardwalk to Grand Geyser or Steamboat Geyser, remember that the pathways leading you to these remarkable features must shift to accommodate the changing landscape that is part of everyday life in Yellowstone.

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