Volcano Updates

Summary

A hazardous hydrothermal explosion occurred in Biscuit Basin on July 23, but it was not associated with any earthquakes and is not an indication of potential future volcanic activity. Yellowstone Caldera activity remains at background levels, with 64 located earthquakes in July (maximum = M2.7). Deformation measurements indicate a pause in subsidence (which has been ongoing since 2015) due to seasonal changes in snowmelt and groundwater conditions.

Recent Work and News

A hydrothermal explosion occurred in Biscuit Basin from Black Diamond Pool on July 23.  This event was caused by accumulation of pressure from boiling water and steam, and it was not associated with any seismic or volcanic activity and does not indicate a heightened potential for a volcanic eruption.  Additional details are given below.

Steamboat Geyser erupted on July 15—its fourth major eruption of the year.  Little activity has been recorded since that time, suggesting that it may be many weeks before the next major eruption.

July field work included deployment of a back country semi-permanent GPS station.  The equipment will be retrieved in September, before the onset of winter makes the area inaccessible.  Geologists also mapped the hydrothermal explosion deposit in Biscuit Basin to better constrain the source depth and mechanics of the event.

Biscuit Basin Hydrothermal Explosion

At 9:53 AM MDT on July 23, a hydrothermal explosion occurred from Black Diamond Pool in Biscuit Basin, about 2.1 miles (3.5 kilometers) northwest of Old Faithful in Yellowstone National Park.  The explosion was caused by liquid water flashing to steam due to changes in pressure conditions within the shallow hydrothermal plumbing system beneath the pool, and it was not related to any changes in seismic or volcanic activity.  Over 1400 rocks with a long dimension greater than 40 cm (16 in) were deposited around the pool by the explosion and surge of water.  The plume of water, steam, and debris was mostly directed to the northeast.  The rocks ejected by the explosion were sandstones, siltstones, and glacial debris that are present within about 50 m (175 ft) of the surface; none of the deeper rhyolite bedrock was found in the deposit.  Many of the rock clasts were coated in silica.  These observations indicate that the explosion was sourced from the shallow hot-water plumbing system just beneath the pool, most likely due to silica accumulation sealing off some of the conduits and leading to the pressure increase.  Nearby hydrothermal features in the basin, like Sapphire Pool and Jewel Geyser, do not appear to have been affected by the explosion, and there was no change in earthquake or ground deformation activity associated with the event.  Hydrothermal explosions are common in Yellowstone National Park, with small ones happening multiple times each year on average.  Explosions of the size that took place on July 23 probably occur once per decade or few decades.

Seismicity

During July 2024, the University of Utah Seismograph Stations, responsible for the operation and analysis of the Yellowstone Seismic Network, located 64 earthquakes in the Yellowstone National Park region. The largest event of the month was a micro earthquake of magnitude 2.7 located about 2.5 miles northwest of West Yellowstone, Montana, on July 21 at 1:34 AM MDT.

July seismicity in Yellowstone was marked by one swarm of 10 earthquakes that occurred July 11–12 and was located about 13 miles northeast of West Yellowstone, Montana.  The largest earthquake in the sequence was a magnitude 1.5 on July 12 at 2:00 AM MDT.

Earthquake sequences like these are common and account for roughly 50% of the total seismicity in the Yellowstone region.

Yellowstone earthquake activity is currently at background levels.

Ground Deformation

During the month of July, continuous GPS stations in Yellowstone Caldera and near Norris Geyser Basin showed a small amount (less than 1 cm, or a fraction of an inch) of uplift.  This deformation occurs every summer and is caused by seasonal changes related to snowmelt and groundwater conditions throughout the region.  Since 2015, Yellowstone Caldera has been subsiding at a rate of about 3 cm (1.2 in) per year, interrupted each summer by a seasonal summertime pause or slight uplift.

An example of GPS data can be found at http://www.unavco.org/instrumentation/networks/status/pbo/data/NRWY (click on Static Plots / Cleaned)