Images

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.

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.

Map of Yellowstone National Park showing the location of major travertine deposits. The green dashed line is the outline of Yellowstone Caldera and red lines are major paved roads.

Travertine sample from the Hillside Springs Group in Upper Geyser Basin, sampled under permit YELL-2020-SCI-8030. (Left) Cut and polished sample slab showing the different layers of travertine; dashed circles indicate where subsamples were taken for geochronology analysis.

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

Visible and thermal maps of Brimstone Basin (top) and Midway / Lower Geyser Basins (bottom).  The images on the left are high-resolution (1-m pixels) visible images acquired by the NAIP program in 2019.  In these images, the extent of the bright white surface cover is visual evidence for the thermal area, and the yellow thermal area boundaries have been di

Map of Yellowstone’s thermal areas.  Thermally active thermal areas (known to have thermal features with above-background temperatures) are shown in red.  Inactive and cold, degassing thermal areas are shown in blue.  Areas that are unknown or inconclusive in terms of their thermal activity are shown in purple.

Outline of the Steamboat and Cistern plumbing systems, with two viewing angles. The structure, color-coded by depth, delineates the observed seismically active area during eruption cycles of Steamboat Geyser. The solid star, solid square, and open triangles denote Steamboat Geyser, Cistern Spring, and seismic station locations on the surface, respectively.

Outline of the Steamboat and Cistern plumbing systems. The structure, color-coded by depth, delineates the observed seismically active area during eruption cycles of Steamboat Geyser. The solid star, solid square, and open triangles denote Steamboat Geyser, Cistern Spring, and seismic station locations on the surface, respectively.

Crinoid fossil from a Paleozoic rock unit found in northern Yellowstone National Park.

Seismic stations (white triangles) around Yellowstone Lake as seen on the online Geology of Yellowstone Map. Inset shows a seismogram for station YLA that can be accessed by clicking on the feature and following the “Seismogram” link in the popup box.

Example of some of the new layers available in the Geology of Yellowstone Map as of early 2021. Shown here are the locations of various monitoring instruments and water sample sites overlain on a thermal infrared satellite image. Lighter colors on the infrared image show more radiant (warmer) areas, whereas dark areas are less radiant (cooler).

Photos from a Scanning Electron Microscope (SEM) showing reacted rhyolite fragments at the end of the laboratory experiments. (a) Image magnified by 500 times showing the rhyolite after it reacted with water at 250 degrees Celsius (482 F). The reacted rhyolite fragments show very little change compared with the unreacted fragments.

Steam vents along the Yellowstone River near Mud Volcano thermal area, Yellowstone National Park.

Mudpot located in the Mud Volcano thermal area of Yellowstone National Park.  This type of thermal feature indicates an acid-sulfate system.

Thermal anomaly map of Yellowstone National Park, based on a Landsat 8 nighttime thermal infrared image from 9 January 2021.  The color ramp indicates the intensity of the above-background thermal anomaly for each thermal area.  Lakes are blue.  Yellowstone caldera and resurgent domes are outlined in black.

Looking southwest from the Steens Mountain summit area into the Alvord desert of eastern Oregon.  This fault-block escarpment reveals the oldest lava flows of the Columbia River Flood Basalts, which erupted about 17 million years ago.  Three or four vertical dikes that feed these flows are evident in the midground ridge where they stand as rock walls cutti

Eruptions of Steamboat Geyser over time.  (A) Cumulative eruptions of Steamboat Geyser since 1960. Each dot represents an eruption. (B) Comparative plot of the cumulative eruptions in each active phase (1960s, 1980s, and 2018-). Data from GeyserTimes.