Images

Modern vegetation on different geological substrates in Yellowstone.  Left: steppe/grassland on glacial clay found in places like Lamar and Hayden Valleys.  Center: Mixed conifer forest in the Absaroka andesite volcanic field in the eastern part of Yellowstone National Park.  Right: Lodgepole pine forest on Central Plateau rhyolite (hydrothermal grass

Vegetation history based on pollen records from three small lakes on different geological substrates in Yellowstone National Park.   Blue is open vegetation, light green is parkland, dark green is forest.  Top plot is from Slough Creek Pond, in a present grassland area dominated by glacial and lake sediment in the northeast part of Yellowstone Nationa

Bathymetric map of the West Thumb Basin showing numerous mapped active or inactive hydrothermal vent sites (small white circles) and sampled hot springs (white stars or larger white circles) and sediment cores (yellow diamonds).  The white-black line represents the 160,000-year-old West Thumb Caldera margin.  West Thumb Geyser Basin is near the southern en

Schematic summary of rhyolite eruptions in the Yellowstone Plateau volcanic field over the past 1.3 million years. Smaller rhyolite eruptions are known intracaldera eruptions, meaning they occurred within existing caldera structures. Additional rhyolite eruptions that occurred outside the caldera are not included in the figure.

Benchmark C9, installed by the US Coast and Geodetic Survey (now the National Geodetic Survey) in 1923 near Apollinaris Spring in Yellowstone National Park.  The number stamped into the mark, “7337.580,” is the elevation in feet that was determined by surveys the year the benchmark was established.  USGS photo by Michael Poland, September 4, 2024.

High-resolution satellite images of Norris Geyser Basin showing the area of Porcelain Basin and Nuphar Lake (both images cover the same area).  In the left image, acquired on April 2, 2024, springs on Porcelain Terrace are full of water, and warm hydrothermal water is flowing into Nuphar Lake from the area circled in yellow.  This warm water kept the north

New steam vent at the base of a hill north of Nymph Lake, west of the highway and between Norris Geyser Basin and Roaring Mountain. USGS photo by Mike Poland, September 1, 2024.

USGS scientists equipped with gas masks and monitors exploring Death Gulch. Photo by Shaul Hurwitz, September 2024.

Wahb Springs in Yellowstone National Park.  Left: zoomed-out photo of the springs (photo by David Roth, September 2024). Right: close-up photo showing the unique organic material floating on the spring water (photo by Shaul Hurwitz, September 2024).

Photo of dead trees along the edge of Nuphar Lake.  The white staining at the base of the trees is a telltale sign that the trees were immersed in thermal water containing silica.  USGS photo by Mike Poland, September 1, 2024.

Looking south from near a pullout along the Mammoth to Norris road just north of the Nymph Lake overlook. On the other side of the marsh is a tree-covered rhyolite lava flow, and at the base of the flow is a new thermal feature marked by a plume of steam and that formed in early August 2024.   Photo by Mike Poland, USGS, September 1, 2024.

Gibbon River near Norris Geyser Basin in Yellowstone National Park at sunset.  USGS Photo by Mike Poland, August 28, 2024.

Professor C.J.N. Wilson, FRS, pays due homage to the Lava Creek Tuff ashfall bed in a basin just east of Shell, Wyoming. Photo by Madison Myers, Montana State University, August 9, 2024.

Looking southeast at the hydrothermal feature that formed in August 2024 just north of Nymph Lake. Steam is emanating from a vent that is partially full of water to create the frying pan feature nestled in the newly formed vent. A thin grey layer of silica mud covers the vent area.  Photo by Jefferson Hungerford, Yellowstone National Park, August 2024.

Plot of size versus annual probability for hydrothermal explosion craters in Yellowstone National Park. The line is a model based on the energy required to form a crater of a specific size, and it is fit to known hydrothermal explosion craters in Yellowstone National Park.

(A) Water distribution in a quartz-hosted embayment measured with synchrotron Fourier Transform Infrared spectroscopy. Warmer colors indicate higher concentrations of water.  Dashed line shows a transect of water content that is modeled in panel (B) to indicate that the emplacement temperature of the ash flow deposit must have been about 500 °C (930 °F).

A clean hand sample of the Mount Jackson vitrophyre. This sample has a black, glassy groundmass with large (1–3 mm, or a small fraction of an inch), white phenocrysts suspended in the glass. Photo by Liv Wheeler, Montana State University, August 2024.

Shaded relief location map for the East Gallatin-Reese Creek fault system (EGRCFS) in northwest Yellowstone National Park (YNP). The location of the EGRCFS is shown as mapped in the U.S.

Abyss Pool is about 16 m (53 ft) deep and contains alkaline-chloride hydrothermal fluids that in the summer of 2024 had a temperature of 181 °F (83 °C).

Mud pots form in a few selected areas of West Thumb Geyser Basin where low-pH acidic fluids dissolve rocks and soil to produce clay-rich muds.  USGS photo by Pat Shanks, 2024.

(A) Photomicrograph of a quartz-hosted embayment from the Mesa Falls Tuff. “MI” indicates a glassy inclusion of melt within the crystal. (B) Thickness (in centimeters) and extent of the Mesa Falls ash flow deposit (pink areas) and its source, Henrys Fork Caldera (dashed line).  Figure by Kenneth Befus, University of Texas at Austin.