Yellowstone Caldera Chronicles is a weekly column written by scientists and collaborators of the Yellowstone Volcano Observatory. This week's contribution is from Beth Bartel, from the non-profit UNAVCO consortium in Boulder, CO.

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Yellowstone is one of the best instrumented volcanoes in the world. There are several dozen GPS stations, seismometers, temperature sensors, river-monitoring sensors, tiltmeters, and strainmeters in the Park alone—and that number doesn't include the many sensors outside the Park! These instruments measure the many changes at Yellowstone--the ground as it moves up and down, or shakes as earthquakes pass through, and the rising and falling temperatures of springs and streams. Yet you will rarely see any of these instruments. Why is that?

If you'd say we keep them hidden, you'd be partly right. The many visitors to Yellowstone every year go to see the thermal features, wildlife, forests, and meadows--not funny-looking bits of metal powered by solar panels! Both research into volcanic processes and a good visitor experience are in the public's interest. So how do we decide where to put these sensors?

First and foremost, any scientific work in Yellowstone National Park happens in close collaboration with Park staff and under Park regulations. No installation or sampling takes place without a permit. Not even a bit of elk poo! The permitting process ensures the Park protects its resources, visitors, and staff. And visitors should be able to appreciate and experience the Park for all its unique beauty and natural richness. Thus, Park staff work with scientists to determine how to best learn about Yellowstone while still protecting it.

This means considering how each instrument or sample will affect the Park. For example, each GPS station, strainmeter, and tiltmeter that measure the movements of the region, including the ups and downs of the caldera, required a site assessment before installation. Would the instrument or its installation disturb important habitat, be visible to visitors, affect water quality, alter thermal features, or damage the traces of people who were here before the Park was established? Scientists and Park staff go back and forth until they find a location that meets both Park regulations and science goals.

The best place for a sensor? Most of the instruments are in non-wilderness areas, off of service roads, in previously impacted areas. The borehole strainmeters, which required drill rigs for installation, were all placed along Park access roads that are off limits to the general public. That's a win-win--it's much easier to service a site that's easy to get to!

But sometimes the things we want to "see" just aren't along the roads. Geology and volcanoes don't care where the roads are!

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The GPS station in Hayden Valley, for example, is not only five miles from a road, but also within a recommended wilderness area. Before installation of that site, named HVWY, Park staff determined that its benefit--the insight it will provide on the activity of Yellowstone--outweighs the cost to its surroundings. The station has a small footprint, and wildlife are more likely to disturb it than the other way around! However, installing a station in a restricted area comes with its challenges. No mechanized vehicles means finding creative ways of lugging heavy equipment.

Since installation, HVWY has mostly been visited on foot. In September of this year, however, HVWY was up for a major renovation. Part of the makeover included swapping out 320 pounds of batteries to keep the station healthy and running year-round. Feet weren't going to be enough for this endeavor, so a team of 18 visited the site: seven humans, seven horses, and four mules to haul the gear. The impact to the Park was minimal, and successful completion of the work means that HVWY will be collecting data for the foreseeable future.

While these instruments might not be pretty, HVWY, like the many other instruments just out of view, enables scientists to track Yellowstone's changes over time--on the surface as well as what goes on underneath. They enable us to see what our eyes can't, all the while hidden from public view. But while you probably won't see YVO stations when you visit the Park, you can see all their data online!