The Surprising Link Between Climate Change and Earthquake Activity

How Climate Change Could Trigger Earthquakes

By Evan Howell edited by Andrea Thompson

The Sangre De Cristo Mountains in Southern Colorado rise sharply from the flat landscape of the San Luis Valley. This impressive geological change was sculpted by the fault system bearing the mountains’ name over millions of years and continues to occasionally shake the region. Recent research indicates that the thawing of alpine glaciers millennia ago might have enhanced the frequency of earthquakes in this area by alleviating pressure on the fault.

Generally, we do not link the Earth’s atmospheric and surface climate with tectonic movements occurring deep within our planet’s enigmatic structure. Nonetheless, the new study, published in Geology, provides rare insights into how rising temperatures—such as those we are experiencing today—might instigate fault activity. As temperatures persist in climbing, scientists warn that other glaciated and seismically active areas could face comparable dangers. “Regions where glaciers are receding, or where alterations in the hydrological cycle are affecting active faults, might experience heightened seismic activity,” states Sean Gallen, a geologist from Colorado State University and co-author of the study.

Approximately 25 to 28 million years ago, the western interior of North America started to diverge, giving rise to the Rio Grande Rift. As the land gradually separated, the San Luis Basin subsided while the Sangre de Cristo range rose, resulting in a vertical displacement of up to 9.2 kilometers between the two portions. Then, around 2.6 million years ago, global temperatures plummeted, leading to the accumulation of glacial ice atop the Sangre de Cristos. The height of glaciation was reached during the Last Glacial Maximum approximately 20,000 years ago, forming dramatic U-shaped valleys and depositing moraines—rubble piles indicating the glacier’s furthest extent.

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Modifications in surface mass can influence the stresses acting upon the Earth’s crust. For instance, when mountains ascend, the crust deforms beneath their mass, similar to a diving board when a person stands on it. As the mountains gradually erode over immense spans of time, the earth rises again. This mechanism, known as isostatic rebound, can induce minor seismic events. This phenomenon explains why relatively ancient mountain ranges like the Appalachians still experience tremors from time to time.

Gallen, along with his co-author Cecilia Hurtado, also from Colorado State University, speculated whether the removal of glacial mass could similarly impact seismic activity. They proposed that the melting of glaciers might alter the stress distribution on faults, possibly accelerating earthquakes in the short term by lightening the burden on the crust.

While computers can easily simulate this behavior, validating the concepts in the natural environment is considered the gold standard, Gallen explains. However, there are limited locations where clear evidence is preserved: for example, the Teton Fault in Wyoming witnessed an increase in seismic activity as the Yellowstone Ice Cap melted. The new study demonstrates that this occurrence may be more prevalent than previously believed by scientists, says Jessica Thompson Jobe, a geologist with the U.S. Geological Survey who was not involved in the study. “It’s quite unique,” Jobe remarks about the research. “They’re attempting to connect climate impacts with fault activity, and this location serves as an excellent case study, as both datasets are available. This is not always the case.”

To substantiate their theory, Hurtado and Gallen constructed computer models based on the physical characteristics of the Sangre De Cristo terrain, including moraines and fault scarps that resemble fissures in the Earth’s surface, offering insight into the timing and location of prehistoric earthquakes. The scientists employed high-resolution lidar (light detection and ranging) and satellite imagery to create detailed maps of these attributes. Finally, they correlated these models with empirical evidence, proposing that glaciers from the Ice Age “secured” the fault system and curtailed earthquake activity. As glaciers began to melt less than 20,000 years ago, the load was lifted, releasing accumulated stress. This led to a remarkable fivefold rise in earthquake occurrences, marking a phase of intensified seismicity compared to the pre-Glacial Maximum state, likely continuing until the glaciers ultimately receded.

Eric Leonard, a geologist emeritus at Colorado College, who did not participate in the study, concurs that the melting of even the relatively small glaciers in the Sangre de Cristos could have profoundly influenced fault activity. He notes, however, that the ages of the faulted surfaces are uncertain, which impacts the accuracy of determining earthquake timing. Gallen acknowledged that employing more precise—and costly—dating methods for the faulted surfaces could enhance the earthquake timeline. However, both he and Hurtado are confident that their findings reinforce previous research from the American West. “We have compelling evidence here,” asserts Gallen.

The authors of the study also caution that areas harboring active faults along with substantial ice or water loads—currently diminishing due to rising global temperatures—may expect an increase in earthquakes moving forward.

Leonard added that a mere three degrees Celsius (5.4 degrees Fahrenheit) spike in temperature caused the majority of ice in the Sangre de Cristos to melt, raising concerns about the larger ice masses present in tectonically active regions, like the Himalayas, the Andes, and Alaska. “Will this significantly enhance hazards?” he questions. “I’m uncertain, but it certainly holds potential.”