Images

Mineral stability diagram showing minerals that are stable under changing temperature and dissolved silica concentrations that are found at and just beneath the floor of Yellowstone Lake.  Two important points illustrated by this diagram are: (1) the minerals that are stable when reacted with vapor-dominated fluids (kaolinite, boehmite) differ substantially fro

A wide array of phototrophic microbial community textures exhibited in an alkaline (pH ~8.5) hot spring outflow channel in the Biscuit Basin, including thick mats, toadstools, ropes, and pinnacles. The differences in color are due to pigments (chlorophylls, bacteriochlorophylls, and carotenoids) produced by phototrophic microorganisms.

Sapphire Pool, an alkaline (pH ~7.5) spring in the Biscuit Basin area of the Upper Geyser Basin, Yellowstone National Park.

An unnamed small acidic (pH ~3) hot spring (with a temperature of about 55°C at the source) in the Gibbon Geyser Basin of Yellowstone National Park. The yellow region is due to the precipitation of sulfur by sulfide-oxidizing chemotrophic microorganisms.

Map of seismicity (yellow circles) in the Yellowstone region during 2019. Gray lines are roads, red line shows the caldera boundary, Yellowstone National Park is outlined by black dashed line, and gray dashed lines denote state boundaries.

Map showing ice cover in the Yellowstone region. Light shaded areas bounded by black and red lines indicate areas covered during the Pinedale (about 20,000-15,000 years ago) and Bull Lake (about 150,000 years ago) glaciations, respectively. Blue lines are contours in thousands of feet on the maximum reconstructed Pinedale glacier surface.

Color-coded map showing the range of helium isotope values across Yellowstone National Park. BC = Boundary Creek, GGB = Gibbon Geyser Basin, MHS = Mammoth Hot Springs.

Contrasting photos of Heart Spring on Geyser Hill in the Upper Geyser Basin from 1998 (left) and 2019 (right). Can you spot differences in the hot spring? Photos courtesy of the National Park Service.

Synchrotron X-Ray microtomography 3D image (a) and cathodoluminescence slice (b) from the same reentrant-bearing quartz crystal from the Lava Creek Tuff. The reentrants are in darker blue in (a) and the black cavities in (b). Note their relationship to quartz growth bands. Red domains are small magnetite crystals.

Maps displaying the stages of evolution of the more recent cycle of volcanism associated with Yellowstone Caldera. From Finn and Morgan, 2002 (High-resolution aeromagnetic mapping of volcanic terrain, Yellowstone National Park).

Color-shaded topographic relief map of the Yellowstone Plateau-Snake River Plain volcanic province showing the track of the Yellowstone hot spot. 

Map panels showing the distribution of major caldera-forming ash-flow deposits from the three major caldera-forming eruptions on the Yellowstone Plateau Volcanic Field. Updated from Christiansen, 2001 (USGS PP 729-G) with new age information.

Models of magma storage. Part (A) depicts the standard model of magma storage—a single, large body of crystal-poor melt, surrounded by crystalline mush. Although this is the standard 'mush' model, geophysical studies fail to find evidence of this type of magma storage at many active systems.

Map showing three types of young faults in Yellowstone National Park. 1) Resurgent dome faults. 2) Volcanism and caldera faults. 3) Basin and Range faults. Courtesy of the Wyoming State Geological Survey.

Summary diagram of the geological record and timing of the Huckleberry Ridge Tuff eruption. See Swallow et al. (2019) for more details.

Rhyolite lavas in the Yellowstone Caldera younger than 631,000 years

Dan Dzurisin, of the Cascades Volcano Observatory, conducting a leveling survey at Newberry Volcano, Oregon, in 2002.

Sulphur Caldron -- an example of an acid-sulfate hydrothermal feature in Yellowstone National Park. Photo taken by Blaine McCleskey, September 2008.

View of Castle Geyser, near Old Faithful, in eruption, taken from the boardwalk, November 5, 2019.

This mountain meadow inhabiting species is generally distinctive in its long copious stem and leaf hairs and inflorescences with congested white to pinkish or light purplish flowering heads that are surrounded by very long stem leaves.

Alpine meadow near Two Ocean Pass on the Continental Divide just south of Yellowstone National Park.