Yellowstone National Park is the site of Earth’s largest concentration of geysers, as well as steam vents, hot springs, and mudpots. These hydrothermal features attest to the region’s volcanic history, which spans over two million years and is the reason that the Yellowstone Volcano Observatory was established. Old Faithful is visible in the upper right corner of this aerial view of the Park’s Upper Geyser Basin. INSET: Heart Spring, also in Upper Geyser Basin, is a pool of near-boiling, blue water about 10 feet across and 15 feet deep surrounded by mats of white sinter and orange-brown algae. National Park Service photos.

(Volcano Watch is a weekly article written by scientists at the U.S. Geological Survey’s Hawaiian Volcano Observatory.)

Hawaiʻi Island’s 2017 Volcano Awareness Month is almost over, and our Volcano Watch series about U.S. Geological Survey (USGS) volcano observatories and their connections to Hawaii is also coming to an end. This week, we visit the observatory that monitors a volcano that produced some of the largest eruptions known on Earth—Yellowstone!

Unlike the other four USGS volcano observatories—Hawaiian (HVO), Cascades (CVO), Alaska (AVO), and California (CalVO)—the Yellowstone Volcano Observatory (YVO) is a “virtual” observatory, meaning that there is no physical building. The observatory presence is mostly online, and the only full-time staff member is the YVO Scientist-in-Charge, who draws on scientists at other USGS observatories and from other institutions to support monitoring and research activities.

YVO was founded in 2001 to strengthen the monitoring of volcanic and earthquake activity in the Yellowstone National Park region (https://volcanoes.usgs.gov/observatories/yvo/).

Initially developed as a cooperative effort of the USGS, National Park Service, and University of Utah, YVO was expanded in 2013 into a consortium of eight organizations: the original three partners, plus universities and state geological surveys in Montana, Wyoming, and Idaho, and UNAVCO (a non-profit university-governed consortium specializing in the study of ground deformation). This collaborative approach to volcano observation ensures better study and monitoring of active geologic processes and hazards.

The YVO consortium shares the burden of establishing and maintaining equipment in the Yellowstone region. For example, the University of Utah operates the Yellowstone seismic network, UNAVCO works with GPS and other deformation data, and the USGS uses temperature and stream gages to track changes in hydrothermal activity throughout the National Park.

As with Hawaiian volcanoes, GPS and satellite radar data indicate deformation of the Yellowstone caldera, and ground-based seismic stations monitor the occurrence of thousands of earthquakes in any given year. Over the past several decades, the caldera has been observed to rise and fall by several centimeters (inches) per year, often accompanied by intense seismicity.

A recent spectacular period of deformation occurred in 2013–2014, when the Norris Geyser Basin area of Yellowstone National Park, on the northwest edge of the caldera, began to uplift suddenly by several centimeters (inches) per year. The uplift lasted until March 30, 2014, when a magnitude-4.8 earthquake occurred—the largest earthquake in the region since 1980!

Immediately thereafter, the region began subsiding. Scientists believe that the uplift was caused by fluid accumulation—probably water or gas—beneath the Norris area. The earthquake represented the breaking of a seal or valve on the hydrothermal system, which allowed the accumulated fluid to drain away and the ground to subside.

It’s worth noting that the same region began uplifting again in early 2016, although the rate was slightly less than that in 2014. In the last few months, the rate of uplift has slowed considerably. No strong earthquakes have occurred in the region thus far.

Although Yellowstone is clearly the focus of YVO’s monitoring and research efforts, the observatory is also responsible for tracking volcanic activity in the Intermountain West, including Montana, Wyoming, Utah, Colorado, New Mexico, and Arizona. Each of these states is home to volcanoes that have erupted within the past few thousand years. For example, Arizona’s Sunset Crater erupted in 1085 A.D., and the McCartys lava flow in New Mexico’s Zuni-Bandera Volcanic Field erupted about 3,000 years ago.

Comparatively little is known about some of the southwestern U.S. volcanoes, and monitoring infrastructure is limited, so YVO supports efforts to better understand this volcanism and its potential hazards. Current and former HVO scientists have been active in interpreting the geologic history of the region, including the basaltic lava flows of New Mexico and the cinder cones of Arizona and Colorado—volcanic areas that bear a striking resemblance to Hawaiian volcanoes.

This marks the end of our series about USGS volcano observatories. But a few more Volcano Awareness Month programs are being offered on the Island of Hawaiʻi: at Hilo’s Lyman Museum on January 30 and February 2, and in Hawaiʻi Volcanoes National Park on January 31. Details are posted on HVO’s website (https://hvo.wr.usgs.gov).

For information about volcanic activity throughout the United States, please visit the USGS Volcano Hazards Program website (https://volcanoes.usgs.gov).