Images

Tuff Cliff, located north of Madison Junction in Yellowstone National Park, is one of the best-known exposures of the Lava Creek Tuff and has long been cited as a classic example of member A of that deposit.  USGS photo by Mike Poland, September 24, 2026.

Black Pearl Geyser in Biscuit Basin, Upper Geyser Basin, Yellowstone National Park.  USGS photo by Mike Poland, September 22, 2026.

YGH monitoring station near Geyser Hill, Upper Geyser Basin, Yellowstone National Park.  Infrasound sensors sit under the brown "hats" that serve as wind screens, and a seismometer is buried nearby.

View from September 11, 2026, at 3:02:16 p.m.

Frequent finds collected by the Yellowstone National Park Geology Team from hydrothermal areas during the summer season in 2026: camera lens covers and binocular parts, pens and pencils, sunglasses, hair accessories, hotel keys, and more!  National Park Service photo by Margery Price, September 2026.

EarthScope intern Lexi Kenis (left) and field engineer Lia Lajoie (right) hike through Hayden Valley in Yellowstone National Park on their way to GPS Station HVWY. Photo by Brendan Hodge, EarthScope Consortium, September 2026.

Hats collected by the Yellowstone National Park Geology Team and other park staff from hydrothermal areas during the summer 2026 season (Geology Team truck for scale). National Park Service photo by Margery Price, September 2026.

Coins, bills, and jewelry collected by the Yellowstone National Park Geology Team from hydrothermal areas during the summer season in 2026.  National Park Service photo by Margery Price, September 2026.

More bizarre Yellowstone National Park Geology Team finds from hydrothermal areas during the 2026 summer season—including golf tees, fortune cookie fortunes, AirPods, rubber ducks, and Invisalign retainers!  National Park Service photo by Margery Price, September 2026.

Acoustic signals recorded at infrasound arrays (red inverted triangles) YBB (in Biscuit Basin) and YGH (near Geyser Hill), in Upper Geyser Basin, can be used to determine the direction from which low-frequency acoustic signals originated, also called the backazimuth.  This example is from 9:14 p.m.

Map of Yellowstone National Park showing Lava Creek Tuff deposits and sample locations. Different colors indicate deposits traditionally assigned to member A (purple), member B (yellow), and the Sour Creek dome (green). Amphibole symbols mark locations where amphibole was identified.

Locations of Lava Creek Tuff samples in the Yellowstone National Park area. Colored rings show the relative abundance of sanidine crystals with different barium (Ba) concentrations, measured in parts per million (ppm), at each site.

Amphibole, which is a mineral that had previously been used to distinguish Lava Creek Tuff (Yellowstone) members A and B.  (a) An amphibole crystal (photo: Rob Lavinsky, iRocks.com – CC-BY-SA-3.0). (b-c) Microscopic images of amphibole crystals from rocks previously assigned to Lava Creek Tuff Member A (b) and Member B (c).

Comparison of changes in seasonal solar radiation (insolation) and the environmental history of Lower Geyser Basin (modified from Whitlock et al. 2026). (A) Insolation anomaly for summer and winter at 45 oN latitude. (B) Pollen-based vegetation reconstructions from Rush Lake (Lower Geyser Basin) and Cygnet Lake (Central Plateau).

View from a research camera installed at Biscuit Basin near the site of seismic, infrasound, and GPS monitoring. The camera has a view of Black Diamond Pool, where a hydrothermal explosion occurred on July 23, 2024, as well as of the area north of the pool where another small explosion occurred on June 13, 2026.  Camera images are updated every 15 minutes

Camera installed at the Biscuit Basin monitoring site. The camera is near the top of a small tower that holds a weather sensor and solar panel that powers nearby seismic and acoustic sensors.  The solar panel that powers the camera is located on the ground at the base of the tower.  USGS photo by Mike Poland, July 22, 2026.

Black Sand Pool, in Yellowstone National Park's Upper Geyser Basin.  The hot spring is known for it's thumping behavior, which occurs every few minutes due to collapse of bubbles within the spring.  The thumping is strong enough to be heard and felt by anyone nearby.  USGS photo by Mike Poland, July 21, 2026.

Aerial view of the Black Diamond Pool area of Biscuit Basin, Yellowstone National Park, showing the locations of northern, middle, and southern vent groups that formed as a result of a small hydrothermal explosion on June 13, 2026.  The "new pool' developed later, between June 14 and 16.

Pool of boiling water that formed a few days after the June 13, 2026, hydrothermal explosion at Biscuit Basin, Yellowstone National Park, and that is located near the middle vent group of features that formed during the explosion.  The pool is about 6.5 × 5.3 meters (21 × 17 feet) in size and formed via collapse based on the lack of surrounding ejecta.

Looking south, toward Black Diamond Pool (steaming blue area in the left middle ground) along a fissure that formed during a small hydrothermal explosion on June 13, 2026, in Biscuit Basin, Yellowstone National Park.  The fissure is about 18.5 meters (61 feet) long and filled with near-boiling water.

Looking downstream along the Firehole River, Yellowstone National Park, from the Midway Geyser bridge on the morning of June 13, 2026.  The milky colors are due to suspended sediment that flowed into the river as a result of a small hydrothermal explosion at Biscuit Basin, which is located a straight-line distance of about 5 kilometers (3.1 miles) upstream.