Images

Plot of temperatures measured by continuous loggers at Guardian Geyser (light red) and Valentine Geyser (dark red) on August 24, 2025. Activity at Guardian Geyser included episodic splashing for a few hours prior to the near-simultaneous eruptions of both geysers just after 6:30 a.m. MDT on this date.  Data collected by Mara Reed, Yellowstone National Park.

Photo of Valentine Geyser and Guardian Geyser in eruption on August 7, 2025. Valentine Geyser is in the rear of the alcove, and Guardian Geyser is at the alcove’s mouth, closer to the camera. Visitors on a trail below the Norris Geyser Basin Museum can be seen at the top of the image. Photo by Carol Beverly, used with permission.

Yellowstone National Park Geology Program volunteer Tara Cross smiles and shows off a pizza box found on Geyser Hill in Upper Geyser Basin. National Park Service photo by Margery Price, August 2025.

A researcher holds a vibrant green sample of thermophilic cyanobacteria collected from a hot spring in Yellowstone’s Lower Geyser Basin. National Park Service photo by Samantha Hilburn, August 2025.

A researcher collects a sample of thermophilic cyanobacteria from a hot spring in Yellowstone's Lower Geyser Basin. National Park Service photo by Samantha Hilburn, August 2025.

Yellowstone National Park Geology Program team member Mara Reed uses a long grabber pole to remove a park map, presumably blown from a visitor's hand or pack by the wind, from a feature in Upper Mammoth Terraces. National Park Service photo by Samantha Hilburn, August 2025.

Yellowstone National Park Geology Program team member Margery Price installs a thermal danger sign near Maiden’s Grave Spring along Fountain Flat Drive. National Park Service photo by Samantha Hilburn, August 2025.

Imperial Geyser in eruption.  The geyser, which apparently formed in 1927, is located in Lower Geyser Basin, Yellowstone National Park.

Fairy Falls, a 200-foot-high (60 meters) waterfall over rhyolite cliffs in the Lower Geyser Basin of Yellowstone National Park.

Debris-flow deposit in the 2024 Elk Fire burn area near Dayton, Wyoming is comprised of poorly sorted, mud- to boulder-sized sediment. A small amount of woody debris is intermixed with the sediment that fills channel.

Runoff during a 2025 summer thunderstorm carried material downstream in this relatively small channel in the High Water Creek watershed within the Elk Fire burn area.

The bark at the base of a tree in a burned watershed in the 2024 Ek Fire burn area has been partially removed by fast-moving water and debris. This damage occurs as debris flows pass through the channel and sediment suspended in the flow scrapes bark off of trees.

Runoff in the 2024 Elk Fire burn area. This meadow near a watershed outlet along Lower Dry Fork Road shows a shallow channel formed during Summer 2025. Although vegetation is recovering, runoff deposited mud and flattened grasses in this low-slope area.

Burned trees and loose material cover a burned hillslope in 2024 Elk Fire burn area near Dayton, Wyoming. Rills, in the foreground formed from rainfall running off the ground surface. New green vegetation shows early signs of postfire recovery.

Knickpoint (a step-like feature in bedrock along stream channel) near the headwaters of a burned watershed in the 2024 Elk Fire burn area near Dayton, Wyoming. The exposed bedrock is heavily fractured, and loose material is visible at the base. During storms, this material can be mobilized and transported downstream.

Postfire debris-flow deposit in a channel within the 2024 Elk Fire burn area near Dayton, Wyoming. Following a July 2025 thunderstorm, the channel filled with mud, cobbles, small boulders, and woody debris. This photo, taken near the watershed outlet, looks upslope from U.S. Highway 14.

Woody debris forms an upstream dam in the 2024 Elk Fire burn area near Dayton, Wyoming. The dam was deposited by a debris flow triggered during a 2025 summer thunderstorm. The woody debris forming the dam is larger and more abundant than material observed lower in the channel.

Burned watershed in the 2024 Elk Fire burn area where a debris flow was triggered during a July 2025 thunderstorm. This downstream view shows the watershed outlet near the Crystal Springs Rest Area and U.S. Highway 14. Heavy equipment used to clear the debris remains on site 8 days after the event.

Postfire debris-flow levee in the 2024 Elk fire burn area near Dayton, Wyoming. This levee, located near the channel margin contains poorly sorted sediment ranging from fine mud-to boulder-sized. A small amount of woody material is also present in the levee. The levee was formed by a debris flow in the watershed, triggered by a 2025 summer thunderstorm.

Close-up view of a debris-flow deposit in the 2024 Elk Fire burn area near Dayton, Wyoming. A debris flow triggered by a 2025 summer thunderstorm deposited poorly sorted material ranging from mud to boulder size. Mud coatings are observed on some larger rocks, and finer material fills spaces between the cobbles and boulders.

Channel in a burned watershed within the 2024 Elk Fire burn area near Dayton, Wyoming where a debris flow initiated during a July 2025 thunderstorm. Near the headwaters, exposed bedrock is visible in channel, and loose sediment and burned trees cover the hillslope above. Trees near the channel margin show damage from the force of the flow.