How climate change can lead to earthquakes

December 23, 2024

3 minutes read

How climate change can lead to earthquakes

Climate change may affect seismic activity, as melting glaciers reduce stress on earthquake-prone faults

Written by Evan Howell and edited by Andrea Thompson

North Creston Creek Valley, a U-shaped valley carved by ancient Colorado glaciers.

The Sangre de Cristo Mountains of southern Colorado suddenly stand out from the flat expanse of the San Luis Valley. The mountain's namesake fault system carved this majestic geographic shift over millions of years and occasionally shakes the region today. A new study suggests that the melting of Alpine glaciers thousands of years ago may also have increased earthquake frequency in this region by relieving pressure on the fault.

We don't usually associate the climate of Earth's atmosphere and surface with the movements of plates miles deep in the mysterious part of our planet. But the new study, published in the journal Geology, provides rare evidence of how high temperatures — like those occurring today — may actually trigger fault activity. As temperatures continue to rise, researchers warn that other icy and earthquake-prone regions may face similar risks. “Areas where glaciers are retreating, or where there are changes in the hydrological cycle due to active faults, may experience elevated seismic activity,” says study co-author Sean Galen, a geologist at Colorado State University.

About 25 to 28 million years ago, the western interior of North America began to divide, creating the Rio Grande Rift. As the land slowly disintegrated, the San Luis Basin sank while the Sangre de Cristo Mountain Range arched skyward, with a vertical shift of up to 9.2 kilometers between the two sides. Then, about 2.6 million years ago, global temperatures dropped, and the peaks of Sangre de Cristos were filled with glacial ice. Glaciation peaked at the Last Glacial Maximum about 20,000 years ago, carving dramatic U-shaped valleys and depositing moraines — piles of rubble that define the maximum extent of the ice.

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The western side of the Sangre de Cristo Mountains, Colorado.

Adding or subtracting surface mass can change the pressures on the Earth's crust. For example, when mountains rise, the crust bends under their weight, like a diving board when someone stands on it. As mountains erode and collapse over time, the land rises again. This process, called isostatic rebound, can cause minor seismic activity. This is why relatively ancient ranges, such as the Appalachian Mountains, still flourish from time to time.

Gallen and his colleague Cecilia Hurtado, also from Colorado State University, wondered whether removing ice mass could similarly affect seismic activity. They hypothesized that melting glaciers might change the pressures on faults, which could accelerate earthquakes in the short term by reducing the load on the Earth's crust.

Computers can model this behavior fairly easily, but testing concepts in nature is the gold standard, Galen says. However, there are a few sites where concrete evidence has been preserved: in one example, the Teton Fault in Wyoming saw more seismic activity as the Yellowstone ice sheet melted. The new study reveals how this phenomenon may be more common than scientists think, says Jessica Thompson Jobe, a geologist with the US Geological Survey, who was not involved in the research. “It's very unique,” ​​Gopi says of the study. “They're trying to link climate to rift activity, and this is a great place to do that because you have information on both datasets. That's not always the case.”

To support their hypothesis, Hurtado and Gallen built computer models based on elemental features of the Sangre de Cristo landscape, such as moraines, as well as fault fissures that resemble cracks in the Earth's skin, which provide clues about the timing and location of prehistoric earthquakes. The researchers used high-resolution lidar (light detection and ranging) technology and satellite images to map these features. Finally, the team compared these models with real-world evidence, and suggested that Ice Age glaciers “tightened” the fault system and suppressed earthquakes. When the glaciers began to melt less than 20,000 years ago, the weight rose and pent-up pressure was released. This resulted in a significant five-fold increase in the frequency of earthquakes, a phase of increased seismic activity compared to pre-glacial peak levels, which likely continued until the glaciers finally retreated.

The slope of the Sangre de Cristo Fault (indicated by the black arrow). The blue lines show the approximate end of glaciers from the last ice age.

Eric Leonard, geologist emeritus at Colorado College, who was not involved in the research, agrees that the melting of even relatively small glaciers on the Sangre de Christos could have a significant impact on rift activity. He adds, however, that the ages of the fault surfaces are uncertain, which affects the accuracy of the earthquake's timing. Gallen acknowledged that more accurate — and expensive — methods for dating fracture surfaces could improve the earthquake timeline. But he and Hurtado are confident that these findings reinforce previous research from the American West. “What we have here is compelling evidence,” Gallen says.

The study authors also warn that areas with active faults and large loads of ice or water — which are now shrinking as global temperatures rise — may experience more earthquakes in the future.

Leonard added that a temperature rise of just three degrees Celsius (5.4 degrees Fahrenheit) has melted most of the ice in the Sangre de Cristos, raising concerns about larger ice masses today in tectonically active regions such as the Himalayas, the Andes and Alaska. . “Would this significantly increase the risk?” He thinks. “I don't know, but it sure has potential.”

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