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Yellowstone—the year 2019 in review

January 6, 2020

Yellowstone Caldera Chronicles is a weekly column written by scientists and collaborators of the Yellowstone Volcano Observatory. This week's contribution is from Michael Poland, geophysicist with the U.S. Geological Survey and Scientist-in-Charge of the Yellowstone Volcano Observatory.

Happy New Year, and welcome to a new decade! We hope that everyone has enjoyed a wonderful start to 2020.

As has become tradition, we would like to take the first Yellowstone Caldera Chronicles article of the year to review what happened in Yellowstone during the previous 12 months. And what a 12 months it was!

Map of seismicity (yellow circles) in Yellowstone during 2019
Map of seismicity (yellow circles) in the Yellowstone region during 2019. Gray lines are roads, red line shows the caldera boundary, Yellowstone National Park is outlined by black dashed line, and gray dashed lines denote state boundaries. Provided by University of Utah Seismograph Stations. (Public domain.)

Steamboat geyser turned a lot of heads in 2018 when it set a new record for eruptions in a single year, with 32. In 2019, Steamboat smashed its own record, with 48 eruptions! The longest period between eruptions was a little over 17 days, while the shortest was 3 days and 3 hours—itself a record for the shortest time between major water eruptions of the geyser. The activity was enjoyed by thousands of park visitors and was the subject of quite a bit of scientific research, which we hope will come to fruition in the coming months.

Unlike 2018, however, there was little additional geyser activity of note. Back in 2018, Ear Spring, near Old Faithful, had a rare eruption, and Giant Geyser, also near Old Faithful, experienced a number of water eruptions. But Giant went quiet in early 2019, with no eruptions after March, and Ear Spring and nearby geysers had returned to their usual level of activity by late 2018. Such is the fickle nature of geysers!

Earthquake activity for the year was overall low. There were 1217 located earthquakes during 2019, which is well below the average of 1500-2500 earthquakes per year. About half of these earthquakes occurred as part of 11 separate earthquake swarms. This is not unusual, since swarms account for roughly 50% of the total seismicity in the Yellowstone region.

Deformation patterns in Yellowstone mostly followed established trends. GPS stations in Yellowstone Caldera showed continued subsidence, with small fluctuations that were probably related to seasonal weather patterns. Since the caldera began subsiding in 2015, both the Sour Creek dome, on the east side of the caldera near Hayden Valley, and the Mallard Lake resurgent dome, on the west side of the caldera near Old Faithful, have subsided by about 10 centimeters (4 inches).

In contrast to the caldera, the area around Norris Geyser Basin had been rising since 2015, but this uplift gradually slowed to a stop in late 2018. After no up or down motion at all during the first 9 months of 2019, the Norris area began to subside in September/October, sinking by about 3 cm (a little more than 1 inch) by the end of 2019.

Aerial view of new thermal area near Tern Lake, Yellowstone.
Aerial view of the new thermal area, in the center left. The existing Tern Lake thermal area is the bright white patch of ground in the upper middle part of the image. West Tern Lake is in the lower right. Research conducted under NPS Geology Programs Milestones Permit 2016-9. (Credit: Michael Poland. Public domain.)

The year 2019 also saw the first visit to Yellowstone's newest thermal area, near Tern Lake on the east side of the caldera. This thermal area was first seen in satellite imagery as a hot spot that was outside any known thermal region. Inspection of older satellite and airborne images revealed that the area was healthy forest as recently as 2001, but then gradually showed signs of tree die-off and chalky white soil, which is characteristic of Yellowstone thermal areas. A team of geologists visited the site during the summer of 2019, finding that boiling temperatures were present just beneath the surface in a few places, and there were vents releasing hot gas that included some hydrogen sulfide (H2S). But there was no water at the surface—no geysers or hot springs.

The past year was also a great one for research, particularly into how earthquakes occur in Yellowstone. For example, multiple studies of the 2017 Maple Creek earthquake swarm were published. These studies concluded that the swarm was largely driven by the migration of water beneath the surface, and was occurring in a region that was prone to seismicity due to the stresses caused by the 1959 M7.3 Hebgen Lake earthquake!

2020 promises to be another interesting year for Yellowstone geology. Stay tuned to future editions of Yellowstone Caldera Chronicles for all the latest about current activity and research results!

We hope that you all had a relaxing and pleasant holiday season. From all the members of the Yellowstone Volcano Observatory consortium, Happy New Year!