WYOMING — Last month, the Wyoming State Geological Survey (WSGS) published a new summary about potential geologic hazards in Wyoming, highlighting threats like earthquakes, landslides, radon and Yellowstone’s volcanic system. Teton County sits in a corner of the state where all of those threats are possible, likely, or have already occurred.
The WSGS strives to study, characterize and circulate information about potential geologic threats, which allows decision makers and the public to prepare for events and conditions. Geologists with the agency study a variety of geologic occurrences and maintain public databases and maps.
“These conditions can occur throughout Wyoming and are an inseparable aspect of the state’s dynamic landscape,” reads the report. “Due to Wyoming’s sparse and rural population, many geologic hazards occur without endangering the public and go largely unnoticed. However, hazards that occur near population centers and infrastructure can pose a serious risk to the health, safety, and economic well-being of Wyoming citizens.”
A majority of earthquakes in Wyoming occur near mountains on the west side of the state. In 2025, there were 1,061 earthquakes recorded with epicenters in Wyoming. The largest was a 3.9-magnitude shake on April 18 in the Gros Ventre Range, which was felt across Teton County but did not cause any damage. According to the report, the U.S. Geological Survey’s National Seismic Hazard Model predicts a greater than 50% chance that parts of Fremont, Lincoln, Park, Sublette and Teton counties will experience a damaging earthquake in the next 100 years. WSGS maintains a database on its website of all earthquakes recorded in the state since the 1970s.
Landslides, another potential hazard, are a familiar occurrence in Teton County, both recently and historically. WSGS has mapped over 33,000 historic and prehistoric landslides across the state. The “catastrophic failure” of Teton Pass in June 2024 was the most significant landslide in recent years. The Gros Ventre Slide, which happened just over 100 years ago, was one of the largest landslides on Wyoming record. WSGS created a high-resolution map of Teton County in 2025 to show different levels of landslide susceptibility.
“The map depicts the relative likelihood of deep-seated, bedrock-involved landslides on a 10-meter grid based on analysis of rock strength and slope angle,” the report states.
Radon is a colorless, odorless, radioactive gas that has been found in test results in all 23 Wyoming counties. It is released by the decay of natural uranium in rock, soil and groundwater, and it can cause lung cancer after long-term exposure to elevated levels. The geological summary states that several locations in the state have a high percentage of tested buildings that exceed the threshold of 4.0 picocuries per liter, including Casper, Jackson, Lander and Sheridan. WSGS partners with the Wyoming Department of Health to map tested radon concentrations across the state.
The volcanic system in Yellowstone National Park (YNP) has also been causing a stir recently, with a major hydrothermal explosion in Biscuit Basin in July 2024. WSGS said in the report that a large caldera-forming eruption is “unlikely on human timescales,” and that more hydrothermal explosions and earthquakes are more likely to be the geologic hazards in YNP. The Yellowstone region is home to the highest number of earthquakes in Wyoming. WSGS also states that there is a potential for “hazard cascades” in the region, when an earthquake can set into motion other hazards like landslides and explosions.
“The historic and geologic records suggest that hydrothermal explosions the size of the Biscuit Basin event occur every 10 to 20 years, while smaller explosions likely occur every year in Yellowstone,” the summary reads.
WSGS works with the Yellowstone Volcano Observatory to better understand the potential hazards in that active corner of the state.
