Rigid, still, immobile — these are some of the words most would use to describe a mountain. But Jeff Moore prefers the verbs “shuddering, shaking, and swaying” instead.
An associate professor of geology and geophysics at the University of Utah, Moore explained that geologists are taught to think about mountains in long time periods, spanning the entirety of Earth’s history. But what if a mountain’s timeline was scaled down to a human timescale?
“We’d have a new way of thinking about these landforms,” he stated in an interview with GlacierHub. “[Mountains] are constantly shuddering and swaying on our time scale. They are alive with vibrational energy.”
Moore has conducted research to back this up. In a study published earlier this year in the journal Earth and Planetary Science Letters, he and a team of researchers tracked how the Matterhorn, a 4,478 meter peak that straddles the borders of Switzerland and Italy, sways to the continual vibration of the seismic activity felt around the world.
Led by Samuel Weber, a geoscientist at the WSL Institute for Snow and Avalanche Research SLF, the study found that the pyramid-shaped Matterhorn’s oscillations are stimulated by earthquakes and energy transferred from ocean movements. Their findings also provide important research implications for tracking and monitoring rockfalls and landslides during earthquakes.
For the past decade, Moore has had a sustained interest in what he calls “charismatic” geological landforms, like rock arches and towers in Utah. The research reported here, however, derives from work from earlier in his career, studying the vibrational properties of large landslides at ETH Zurich in Switzerland. When he returned to the university in 2019 on sabbatical, he met up with Jan Beutel, a computer scientist now at the University of Innsbruck in Austria, who’s been studying the Matterhorn for over a decade. Together, the team of interdisciplinary researchers aimed to communicate how and why the Matterhorn sways, Moore explained.
Glaciers once carved the Matterhorn’s unique peak, called a glacial horn, making it one of the most recognizable and photographed mountains in the world. The Matterhorn’s extreme geometry is also what inspired the researchers, challenging them to study hard-to-reach points on the mountain, including the summit, to understand how the mountain was impacted by continual seismic vibrations.
Although the study offers a complex understanding of geology and geophysics, Moore reiterated that vibrations are something everyone experiences day to day. When excited, every object vibrates at certain frequencies — a bridge shakes as cars drive over it and a guitar string quivers as a finger plucks it. The team of researchers applied this same theory to the Matterhorn. Weber was also “fascinated by the idea that a mountain is singing,” he told GlacierHub, wondering if “we can record it and how does it sound?”
A day of continuous ambient vibration data recorded from the summit of the Matterhorn, sped up 80 times to become audible. Courtesy of Samuel Weber
To record the Matterhorn’s vibrations, the researchers placed seismometers about the size of coffee mugs at several locations on the mountain. Via helicopter, they placed one device at the summit, another under a small floorboard in the Solvay Hut, an emergency shelter on the northeast ridge, and one at the mountain’s base for reference, Weber explained. The seismometers streamed ambient vibration measurements to a logger, which the researchers then sped up 80 times to make the mountain’s resonant frequencies audible.
Their findings also revealed that the Matterhorn oscillates in various directions. A perfectly symmetrical skyscraper, for example, will sway in each direction at the same frequency, Moore explained. This was also the case for the Matterhorn, which has a unique pyramid shape, moving back and forth from east-west and north-south directions at similar frequencies of just micrometers to nanometers. However, if there is an earthquake, this movement will become more dramatic. The seismometers also revealed that the Matterhorn was stimulated by more than just earthquakes, but also ocean activity, known as the microseism, a seismic oscillation generated by the interaction of ocean swells and coasts and propagated inland.
The study has important implications for monitoring rock slope dynamics during an earthquake. During the 2010 Haiti earthquake, for example, there was more damage to rock formations on ridges than there was in valleys because seismic energy is amplified on ridges, explained Moore. The researchers’ findings confirmed this. At the summit, the Matterhorn’s measured movements were 14 times stronger compared to the mountain’s base. Although the researchers focused on the movements of the Matterhorn, their new understanding can be applied to mountains around the world.
“This is something all mountains are doing, from the lowest hill to the Matterhorn,” Moore said. Studying the Matterhorn provided a basis for extremes of topographic amplification and vibrations, giving other researchers and geologists a spectrum of how mountains will respond to seismic activity and information to help communities better prepare for landslides, rockfall and rock damage which can impact climbing routes and tourism.
The researchers’ diverse expertise in geology, geophysics and computer science was key to the study’s success, showing the importance of interdisciplinary collaborations, according to Weber. To Moore and his colleagues, this research counteracts the common idea that mountains are stand-alone, autonomous landforms that evolve in periods of billions of years. Instead, they are intimately linked to the world in ways beyond the human sense. “Just because we can’t experience it, feel it, hear it or see it, doesn’t mean it’s not real,” Moore concluded.
Editor’s note, March 24, 2022 at 1pm ET: A previous version of this story stated that the frequency of the Matterhorn’s movement increases as a result of earthquakes; in fact, the frequency stays the same but the amplitude increases. We have amended the text to reflect this.