UTA Research Helping Pinpoint Occurences of Hydrothermal Explosions

Thursday, Jun 18, 2026 • Greg Pederson :

Karissa Cordero at Valles Caldera Nature Preserve in New Mexico. (Courtesy of Karissa Cordero)

Hydrothermal explosions, which occur when superheated water below the Earth’s surface rapidly converts to steam and erupts from the surface, can happen with little or no warning. Determining when explosions happened is important because it helps geologists understand the conditions that triggered them.

Accurately dating past hydrothermal explosions is difficult. One technique, known as luminescence dating, has shown great promise as a tool to reveal when past hydrothermal explosions occurred. This method is the subject of a new article authored by Karissa Cordero, a UTA Ph.D. student in Earth and environmental sciences.

The article, published on the United States Geological Survey (USGS) website, is titled “No longer in the dark: Shining a light on Yellowstone’s hydrothermal explosions” and is part of the weekly Yellowstone Caldera Chronicles series. The Yellowstone Plateau Volcanic Field, located in Yellowstone National Park, is an active landscape with a history of large volcanic eruptions and hydrothermal explosions.

“Luminescence dating is used to determine the last time sediment grains were exposed to heat or sunlight,” Cordero said. “While sediments and rocks are resting on the Earth’s surface, they are exposed to natural ionizing radiation from their surroundings. This radiation causes electrons to become trapped within defects in the crystal lattices of minerals such as quartz and feldspar. When the minerals are later exposed to sufficient heat or light, the trapped electrons are released, producing the luminescence signal.”

In the laboratory, these signals are measured and compared to the natural radiation doses the samples contained when they were collected. In the case of hydrothermal explosions, the method is used to determine the last time sediment grains were exposed to intense geothermal heating associated with an explosion, which provides an estimate for the age of the explosion.

The work was conducted in the lab of Nathan Brown, UTA assistant professor of Earth and environmental sciences and Cordero’s faculty advisor. Samples were collected by Cordero, Brown and their USGS collaborators during two field seasons in Yellowstone.

“To prevent unwanted light exposure, the samples were collected under light-safe conditions in the field, which involved hammering metal tubes into the sides of the explosion craters to preserve the natural luminescence signal,” Cordero said. “The samples were then transported to the luminescence laboratory at UTA, where I processed them to isolate potassium feldspar (K-feldspar) and pure quartz grains for analysis. Once isolated, the grains were mounted onto our luminescence instrument that administers controlled doses of radiation and stimulates the minerals using either light or heat. By measuring the resulting luminescence signal, we can determine the time since the grains were last exposed to heat or sunlight.”

Cordero said that one of the goals of the project is to help in identifying the driving mechanisms behind these hydrothermal explosions. In the case of the Yellowstone study, the team found evidence that some of the larger explosions were likely linked to glacier retreat during the Pinedale Glaciation, Yellowstone region’s last major glaciation, which lasted from around 30,000 to 10,000 years ago. As glaciers retreated, changes in pressure and groundwater circulation may have destabilized the hydrothermal system and contributed to explosive activity.

“Understanding both the timing and causes of these explosions provides important insights into the subsurface temperature, pressure, and hydrothermal circulation conditions that precede such events,” she said. “This information ultimately contributes to volcanic and hydrothermal hazard assessments in Yellowstone and helps improve safety for park visitors.”

The team’s broader goal is to use the techniques developed for the Yellowstone hydrothermal explosion deposits to study phreatic and phreatomagmatic eruptions in volcanic systems around the world. Phreatomagmatic eruptions result from magma erupting through water, while phreatic eruptions result when water beneath the surface is heated by volcanic activity and once heated, begins to boil or even flashes straight to steam, causing an explosion.

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