Michael Poland

Frying Pan Lake (also called Waimangu Cauldron), in New Zealand, sits within Echo Crater, which formed during the 1886 eruption of Tarawera.  A hydrothermal explosion from the crater in 1917 resulted in the formation of the hot spring "lake" by 1918.

Geology of the unconformity on Mount Everts in Yellowstone National Park.  Sketch at the top was made by geologist William Henry Holmes in 1878 and correctly identifies Cretaceous sediments overlain by much younger rhyolite rocks, including fine ash deposits (“tufa”).  The photo at the bottom shows the same outcrop as viewed from Mammoth Hot Springs (USGS

Map of seismicity (red circles) in the Yellowstone region during 2022. Gray lines are roads, black dashed line shows the caldera boundary, Yellowstone National Park is outlined by black dot-dashed line, and gray dashed lines denote state boundaries.

Google Earth image of the north part of Lower Geyser Basin showing the site of the Fountain Hotel and nearby Leather Pool, which was tapped to provide a source of hot water for the hotel.

Interferogram created from data collected on September 29, 2021, and October 6, 2022, by the Sentinel-1 satellite system. Colored fringes indicate a change in distance (called range change) between the satellite and ground surface that is caused by surface deformation.

Front cover of the Yellowstone Volcano Observatory’s Volcano and Earthquake Monitoring Plan for the Yellowstone Caldera System, 2022–2032.

Map of SNOTEL snowpack telemetry sites (blue dots) and streamgages (red dots) in and around Yellowstone National Park.

Yellowstone River level (left) and discharge (right) during June 9–16, 2022, measured at the Corwin Springs streamgage just north of Yellowstone National Park (https://waterdata.usgs.gov/mt/nwis/uv/?site_no=06191500&PARAmeter_cd=00065,00060,00010).  The

Panoramic image of Valles Caldera, New Mexico, looking at the Valle Grande, part of the calderas “moat.”  The resurgent dome is the high topography at the left side of the image, while the hills at the center and right are lava domes.  USGS photo by Mike Poland, June 10, 2022.

Panoramic image of the Sulphur Springs thermal area in Valles Caldera, New Mexico.  The altered surface, composed of clays, strongly resembles acid-sulfate thermal areas in Yellowstone National Park, like the Mud Volcano region.  USGS photo by Mike Poland, June 10, 2022.

The Bandelier Tuff near Los Alamos, New Mexico.  The Jemez Mountains, home to the Valles and Toledo calderas where the tuff originated, rise in the distance.  The tuff was hot and thick when it was deposited by caldera-forming eruptions 1.61 and 1.25 million years ago, and so it is welded in places, forming a dense and resistant rock.  USGS photo by M

Scientists install a semipermanent GPS station in Yellowstone National Park.  These stations, which are not radio-telemetered, are typically installed in May and recovered in October, when the data are downloaded and processed.  These stations help to supplement the continuous GPS network in the Yellowstone area.