Images

Schematic illustration showing the 1912 Novarupta eruption in Alaska and the caldera collapse at Mount Katmai, 10.6 km (about 6.6 miles) to the northeast.

Mount Epomeo on the island of Ischia. The visible western slope of the resurgent block consists of 55,000 year old rocks that formed one of the most widespread Late Quaternary pyroclastic deposits in the Mediterranean region.  INGV photo (https://www.ingv.it/en/Ischia).

View from the SE rim of McDermitt caldera, Nevada and Oregon, showing rhyolite lavas overlain by thin outflow McDermitt Tuff in the south wall of the caldera. The low area that makes up most of the photo is intracaldera tuffaceous sediment. This is Thacker Pass, the site of largest and highest-grade lithium deposits in the region.

Folds in outflow sheets of McDermitt Tuff, from the eruption that formed McDermitt Caldera in Nevada and Oregon about 16.4 million years ago.  The folding is called “rheomorphism” and occurred as the hot ash deposit flowed under its own weight shortly after it was deposited over preexisting topographic highs and lows.  The texture resembles that of rhyolit

Steam rises above a hot pool at Agua Shuca, one of many thermal areas of the Ahuachapán geothermal field of El Salvador. A sudden hydrothermal explosion at Agua Shuca in October 1990 ejected steam and debris within a 200-m-radius, and about 25 people living adjacent to the thermal area were killed.

Yellowstone National Park employees Rick Hutchinson (right) and Jim Peaco (left) guide the specially designed Little Dipper boat into the boiling waters of Grand Prismatic Spring to collect measurements of the temperature and structure of the feature. National Park Service photo by Josh Robbins in 1996.

Queen's Laundry bathhouse, in the Lower Geyser Basin of Yellowstone National Park.  Building began under superintendent Philetus Norris in 1881 but was never finished.

Cross section of the Western Snake River Plain, Idaho.

A gas plume rises above lava fountains in a lava lake in the summit crater of Nyiragongo volcano on 20 August 1994. USGS photo by Jack Lockwood.

Photo of a deep-ocean hydrothermal vent system from the East Pacific Rise at 9º39’N latitude and 2550 m (8366 ft) depth showing vigorously venting “black smoker” hydrothermal fluids (329 °C, or 624 °F) that are dark gray to black due to rapid precipitation of iron, copper, and zinc sulfide minerals as the hot water mixes with cold bottom waters.

Color-shaded relief topographic map of the track of the Yellowstone hotspot showing the ages and locations of volcanic fields and faulting patterns which become younger to the northeast.  Areas in cooler colors (greens and blues) represent low topographic elevations, whereas warmer colors (oranges and reds) represent high elevations.  Adapted from

Porkchop Geyser erupting in August 1989.

Ice cone at Porkchop Geyser in March 1989.

La Garita Mountain (elevation 4179 m [13711 ft]), Colorado.  The mountain is a resurgent block of Fish Canyon Tuff that is more than 1 km (0.6 mi) thick—the top is eroded and the base is not exposed.  The tuff formed during the eruption of La Garita caldera about 27.8 million years ago and has a volume of more than 5000 km³ (1200 mi³)

Mount Vesuvius behind city of Naples. The modern cone of Vesuvius is flanked on the left by Monte Somma, the rim of a caldera that formed about 17,000 years ago. Eight major explosive eruptions have occurred since, including the 79 CE eruption that destroyed Pompeii and other towns.

Novarupta Dome, with Falling Mountain and the upper valley portion of the Valley of Ten Thousand Smokes in the background.  Photo by Tom Miller, June 1979.

USGS scientist Irving Friedman (1920–2005) was an adventure enthusiast. Here he is preparing for a dive with his longtime USGS colleague Peter Lipman at Makalawena Beach, north of Kailua-Kona on the Island of Hawai’i, in 1977. Photo by Peter Lipman.

Photo of damage to the Mammoth-Norris highway, just south of Mammoth Hot Springs, caused by the June 30, 1975, magnitude-6 earthquake.  Haynes Inc. photo for the Deseret News.

Gibbon River in Gibbon Meadows immediate following the June 30, 1975, magnitude-6 Yellowstone National Park earthquake.  The muddy color is due to increased sediment load.  NPS photo by Rick Hutchinson.

Muddy thermal discharge (foreground) near Congress Pool (middle ground) in Norris Geyser Basin following the June 30, 1975, magnitude-6 Yellowstone National Park earthquake,  NPS photo by Rick Hutchinson.

Map: Index map showing locations of 1967–1968 research drill holes in Yellowstone National Park. Taken from USGS Bulletin 1967.