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.

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.

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.

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.

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.

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.

This photo shows Halema‘uma‘u Crater from the western caldera rim, looking east. Active surface lava is limited to the western portion of the lake, and can be seen as the silvery surface just below the center of the image. The eastern portion of the lake is solidified at the surface, and is visible just above the center. USGS photo by M. Patrick.

This photo was taken from the western caldera rim, and looks down up on the western fissure supplying lava into the lake in Halema‘uma‘u, at the summit of Kīlauea. Incandescence is visible in a small vent opening in the lower left portion of the image. In the upper right, the lava stream at the lake inlet slowly flows eastward. USGS photo by M. Patrick.

The western fissure remains active, supplying lava to the lava lake in Halema‘uma‘u Crater, at the summit of Kīlauea. This photo shows a close-up of the inlet where lava enters the lake. The motion of the lava stream has been slow but continuous. USGS photo by M. Patrick.

The lava lake in Halema‘uma‘u crater, at the summit of Kīlauea, remains active. The active surface lava lake, shown in this photo, is limited to the western portion of the lake between the western fissure complex (center left) and the main island (right).

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.

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.

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

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).

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.

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.