Images

Gravity coring device on the rear deck of the R/V Annie after coring the floor of Yellowstone Lake, with dark mud coating the outside of the corer.  The 100-lb. green coring head is at the top, and the bottom of the barrel has a tapered stainless steel core cutter.

View to the aft of the R/V Annie as it leaves Bridge Bay Marina early in the morning of August 26, 2021.

A hand-sample photo of what is known to be Lava Creek Tuff “unit 2.”  Small black scoria pieces are distinctive of this unit compared to the previously recognized Member A and Member B of the Lava Creek Tuff.  Photo by Ray Salazar (Montana State University) on August 16, 2021.

Schematic displaying the general processes associated with collapse of Yellowstone Caldera.  (A) Pre-caldera volcanism includes the eruption of dome complexes from the underlying magma chambers.  (B) The caldera-forming eruption evacuates a significant amount of magma from the chamber, causing the overlying crustal block to subside into the void space.&nbs

“Hey Bear” volcano, Wyoming, with Raggedtop Mountain in the background. Hey Bear volcano is a small scoria cone that is about 1.3 million years old and that erupted over Eocene (~50 million-year-old) rocks (noted by yellow dotted line). Photo by Matthew Brueseke, Kansas State University, August 2021, used with permission.

Photograph of Twin Buttes in Lower Geyser Basin looking to the northwest, with Excelsior Geyser of Midway Geyser Basin in the foreground. Twin Buttes is a thermal kame that formed when glaciers covered the area, and hydrothermal activity below the ice led to melting and the deposition and cementation of glacial sediments.

The Yellowstone borehole geophysical network, installed by UNAVCO in 2007–2008. The placement of the boreholes is focused primarily around the caldera, and the boreholes contain a mix of instruments, including strainmeters, seismometers, tiltmeters, and pore pressure sensors.

Imperial Geyser, Lower Geyser Basin, Yellowstone National Park. USGS photo by Lauren Harrison, July 2021.

Visible and thermal infrared images of Yellowstone acquired on July 17, 2021.  In the visible image, Landsat 8 channels 4-3-2 are assigned red-green-blue colors (respectively) to simulate natural color.  In thermal infrared image, bright pixels are warmer, and dark pixels are cooler.  The full satellite images are clipped to the boundaries of Yellowst

Seismogram from station YTP in Yellowstone National Park showing earthquakes from the swarm beneath Yellowstone Lake that began late on July 15, 2021. Each row represents 30 minutes of seismic data.

USGS scientists Laura Dobeck and Sara Peek carrying field equipment to set up a gas monitoring station in Yellowstone National Park. USGS photo by Jennifer Lewicki, July 13, 2021.

Geologic block-diagram and conceptual model of possible flow systems associated with thermal areas at Mammoth Hot Spring (MHS) area from Sorey (1991) (USGS Water-Resources Investigations Report 91-4052).  Also shown are the Bear Creek Hot Springs (BC) and La Duke Hot Spring (LD).

Epicenters of 6,188 earthquakes in the Hebgen Lake region since 1990 determined by the University of Utah Seismograph Stations and the Montana Bureau of Mines and Geology. All epicenters have horizontal uncertainties of 1.0 km or less.

Map of Yellowstone National Park showing the major rivers and the continental divide (red dashed). Yellowstone Caldera is oulined by purple dashed line. Water flowing south and west of the divide ends up in the Pacific Ocean, whereas water north and east of the divide ends up in the Gulf of Mexico.

Upper map shows the flow path of hot spring water from the Old Faithful area through the Firehole, Madison, Missouri and Mississippi Rivers to the Gulf of Mexico. Lower map shows the flow path of hot spring water from south of the continental divide through the Lewis, Snake and Columbia Rivers to the Pacific Ocean.

Comparison of Porkchop Geyser in September 1984 (left) and August 1986 (right).  The Geyser entered a period of near-constant eruption in 1985, and the pool disappeared; it exploded on September 5, 1989.

Simplified cartoon showing differences between patterns of earthquakes expected for a swarm driven by a magma-filled crack (left) versus one driven by pressurized water in a fault (right).

View of Monument Geyser Basin in Yellowstone National Park, with one of the silica spire "monuments" (from which the basin gets its name) in the foreground. USGS photo by Mike Poland, May 15, 2021.

Roaring Mountain, an acid-sulfate thermal area about 5 miles south of Norris Geyser Basin along the Norris-Mammoth road.  At times during the late 1800s and early 1900s, the sound of gas escaping from vents could be heard over a mile away, but today the thermal area is mostly quiet, although remains intensely hot with over 100 megawatts of geothermal radiative

Photographs of the two dominant rock types found on Mount Everts: the Everts Formation (photo by Natali Kragh, May 18, 2021) and the Landslide Creek Formation (photo by Emma Kerins, May 2021). Notice the difference in scale between these two units, indicated by the pencil and field book.

Photographs of travertine in Yellowstone. A) Travertine terraces actively forming at Mammoth Hot Springs.