YELLOWSTONE VOLCANO OBSERVATORY MONTHLY UPDATE
U.S. Geological Survey
Friday, October 1, 2021, 1:32 PM MDT (Friday, October 1, 2021, 19:32 UTC)
44°25'48" N 110°40'12" W,
Summit Elevation 9203 ft (2805 m)
Current Volcano Alert Level: NORMAL
Current Aviation Color Code: GREEN
Recent work and news
Yellowstone Volcano Observatory scientists are gearing up for some of the last field work of the 2021 season. In the coming weeks, geophysicists will be conducting maintenance on the Norris temperature network to ensure that it remains operational throughout the winter, and also conducting a gravity survey, done every year to help detect changes in mass beneath the ground. They will also be recovering the 17 sites of the semipermanent GPS network—a set of temporary sites that supplement the continuous GPS network during summer months. These stations are deployed every May, after much of the snow melts, and are collected every October, before winter sets in. The GPS receivers are not connected to any radio telemetry, so they must be recovered to download and examine the data. The sites will be redeployed in May 2022.
After taking a month off, Steamboat Geyser erupted twice in September—on September 11 and 28—bringing the total number of eruptions for the year to 15. Eruptions are irregular and much less frequent than during the previous three summers, which may indicate that the geyser is trending toward a period of quiescence. This is typical behavior for Steamboat, with the geyser experiencing few-year periods of frequent eruptions separated by years to decades of very few eruptions.
During September 2021, the University of Utah Seismograph Stations, responsible for the operation and analysis of the Yellowstone Seismic Network, located 283 earthquakes in the Yellowstone National Park region. The largest event of the past month was a minor earthquake of magnitude 3.2 located 15.6 miles south of Old Faithful, Yellowstone National Park, on September 8 at 11:01 AM MDT.
September seismicity in Yellowstone was marked by 4 earthquake swarms.
1) A series of 153 earthquakes ~14 miles north-northeast of Old Faithful began September 16 and continued to the end of the month. The largest event (magnitude 1.8) occurred on September 22 at 06:53 PM MDT.
2) A small swarm of 17 earthquakes ~8 miles north-northeast of West Yellowstone, MT, began September 28 and continued to the end of the month. The largest event (magnitude 1.5) occurred September 29 at 07:42 MDT.
3) A small swarm of 16 earthquakes began September 29 and continued to the end of the month beneath Yellowstone Lake ~0.5 miles southwest of Dot Island. The largest event (magnitude 1.9) occurred September 30 at 00:05 AM MDT.
4) A small swarm of 14 earthquakes occurred September 8, located ~15.5 miles south of Old Faithful. The swarm included the largest event of the month (magnitude 3.2; detailed above).
Earthquake sequences like these are common and account for roughly 50% of the total seismicity in the Yellowstone region.
Yellowstone earthquake activity remains at background levels.
Subsidence of Yellowstone Caldera, which has been ongoing since 2015, has paused during the summer months, reflecting seasonal groundwater recharge. Every summer, water from snow melt causes the ground to swell slightly, resulting in a pause in subsidence trends or even a minor amount of uplift (less than 1 cm / fraction of an inch). In the area of Norris Geyser Basin, no significant uplift or subsidence has been detected by a nearby GPS station since the start of 2020.
An example of GPS data can be found at http://www.unavco.org/instrumentation/networks/status/pbo/data/NRWY (click on Static Plots / Cleaned)
The Yellowstone Volcano Observatory (YVO) provides long-term monitoring of volcanic and earthquake activity in the Yellowstone National Park region. Yellowstone is the site of the largest and most diverse collection of natural thermal features in the world and the first National Park. YVO is one of the five USGS Volcano Observatories that monitor volcanoes within the United States for science and public safety.
YVO Member agencies: USGS, Yellowstone National Park, University of Utah, University of Wyoming, Montana State University, UNAVCO, Inc., Wyoming State Geological Survey, Montana Bureau of Mines and Geology, Idaho Geological Survey
Michael Poland, Scientist-in-Charge