Since 2017, the Yellowstone Volcanic Observatory has been releasing annual reports that contain a wealth of information on a variety of topics – such as ground deformation trends, earthquake activity, and monitoring network upgrades. In addition, there is information on research results and new discoveries, such as the recognition of a new thermal zone near Tern Lake in 2018.
The Yellowstone Volcano Observatory’s 2022 annual report has just been released and is now available online.
As in previous years, the summary highlights monitoring data collected throughout the year. For example, the Yellowstone region recorded 2,429 earthquakes in 2022, the largest of which was a magnitude 4.2 earthquake on May 11, the largest earthquake in the area since a magnitude 4.4 earthquake in 2017.
The number of earthquakes is within the normal range of annual events and slightly less than in 2021. About 66% of the earthquakes occurred as swarms, which are groups of earthquakes grouped together both in space and time. The most significant swarm, which had more than 1,100 earthquakes and lasted throughout the second half of the year, occurred near Grizzly Lake, between Mammoth Hot Springs and Norris Geyser Basin. Clusters of earthquakes with hundreds and thousands of events lasting months are not unusual in the Yellowstone region and occur every few years.
Similar to the trend since 2015, the Yellowstone caldera sank 1 to 2 inches over the course of the year, punctuated by a pause in the subsidence during the summer months or a slight rise when the ground subsided slightly due to groundwater recharge from snowmelt. Little significant deformation has been detected in the Norris Geyser Basin area since 2018.
Speaking of water, Yellowstone had a lot of it in 2022 — an atmospheric river event in mid-June dumped several inches of rain on the late-season snowpack, causing catastrophic flooding in the Yellowstone region and temporarily closing the entire park. Access roads from the north and northeast were inaccessible until late summer due to flood damage. Yellowstone Volcanic Observatory monitoring stations, some of which did record seismic noise associated with floodwaters, were largely intact, except for one river monitoring station along the Gardner River in the northern part of the park, which was buried under several feet of debris.
All that water didn’t seem to have much of an effect on Yellowstone’s hydrothermal system — there was no significant change in the behavior of most of the geysers. Steamboat Geyser, the tallest active geyser in the world, has erupted 11 times in 2022, continuing a trend of frequent activity that began in 2018. The number of annual eruptions has been declining since a peak of 48 eruptions in 2019 and 2020, but it is increasingly likely that the current period of many eruptions is coming to an end.
The chemical composition of gas and water and emissions have not changed significantly compared to previous years. A new continuous sensor capable of measuring carbon dioxide emissions has been installed in the mud volcano area, and expeditions have been conducted to measure gas and water chemistry in several areas of the park—including the new thermal area near Tern Lake. There, geochemists discovered that much of the earth is at boiling point just below the surface. Carbon dioxide emissions were elevated relative to background, but were negligible compared to similar thermal zones—about half that of the mud volcano region, when accounting for, for example, the difference in size of the two thermal zones.
Research into the causes and effects of hydrothermal vents in Yellowstone National Park has focused on the northern part of Yellowstone Lake and the Upper Geyser Basin.
Sediment cores from the bottom of Yellowstone Lake have revealed many thin layers of crushed rock that are evidence of steam explosions of various sizes that have occurred over the past 14,000 years. The largest explosions occurred in hydrothermal zones with neutral chloride, where the transition from liquid water to steam was associated with rapid expansion of the liquid, causing significant explosions.
In contrast, steam-dominated hydrothermal areas do not experience this phase transition and are therefore incapable of large steam explosions. The largest eruptions in the Yellowstone Lake area, from Mary Bay and Elliott Crater, were likely associated with lake-floor earthquakes that altered the pressure conditions in the lake-floor hydrothermal systems. Similar triggers are also believed to have caused steam explosions in the upper basin of the geysers. There, sudden collapses of loose mounds of glacial debris deposited on hydrothermal vents by retreating ice during the last ice age would have altered the pressure conditions deep in the surface, causing the water to erupt into steam, rapidly expand, and lead to explosions.
Scientists at the Yellowstone Volcano Observatory will also learn more about the intricacies of the great volcanic explosion that formed the Yellowstone Caldera 631,000 years ago. The ash deposit that formed from this explosion, called the Lava Creek Tuff, was originally thought to be composed of two geological subunits.
However, Montana State University geologists identified several new pieces of the Lava Creek Tuff while mapping rocks on the Sur Creek Dome on the east side of the Yellowstone caldera. This discovery means that the eruption was much more complex than previously thought, and more work is needed to understand the details of the eruption’s history.
As usual, monitoring data and research results continue to open new avenues for better understanding of Yellowstone’s volcanic, seismic, and hydrothermal behavior. The Yellowstone Volcano Observatory will look to expand on these results in 2023 — fieldwork is already underway!
Yellowstone Caldera Chronicles is a weekly column written by scientists and staff at the Yellowstone Volcano Observatory.