Timeless Melodies from Ancient Stone Arches

This could be described as the ultimate classic rock music. Forget the Rolling Stones — in the Southwest deserts, it's the ancient rocks themselves that are crafting eternal harmonies.

Explore areas like Arches National Park or Grand-Escalante National Monument, and you'll encounter rock arches in countless forms and dimensions. These natural marvels are far from motionless; they vibrate and adjust throughout the day, generating a symphony of sounds as they flex their ancient, weathered structures, shifting and settling in ways reminiscent of a vibrating guitar string.

The wind causes them to resonate at specific frequencies. Similarly, distant earthquakes, passing vehicles, aircraft, and even ocean waves hundreds of miles away can trigger vibrations. By analyzing the resonant frequency of a particular arch over time, scientists can identify changes that may signal cracks or shifts in the rock's stability. (Listen to a recording in the tweet link below.)

Under the guidance of University of Utah geologist Jeff Moore, researchers place one broadband seismometer on an arch and another approximately 328 feet (100 meters) away on stable, flat ground. Over time, they compare the data to isolate and pinpoint the arch's unique resonance.

"We are currently tracking around 20 arches in total. Some are measured frequently, others less so, and at one site, we continuously monitored ambient vibrations and spectral properties for over a year," Moore explained in an email interview.

While studying hundreds of arches across three national parks and two national monuments, Moore's team occasionally deploys up to 36 nodal seismometers at a single location to capture the ambient resonance of structures like Musselman Arch. They've discovered that each arch has its own unique movement, resonating in harmony with its surroundings.

Humans cannot perceive these vibrations with their senses. However, with specialized equipment and some audio engineering expertise, the rock "songs" become audible. Larger arches produce deep, rumbling tones, while smaller ones may emit higher-pitched, squeaky sounds.

"We've truly enjoyed collaborating with artists who use vibration recordings as a fresh way to experience red rock arches as vibrant, ever-changing natural wonders," Moore shares.

Beyond seismometers, researchers also employ tiltmeters and thermometers to monitor the arches. For instance, during midday, intense desert heat causes thermal expansion in the rock, leading to subtle swelling and tilting. As temperatures drop at night, the rock contracts, much like the creaking timbers in an aging house.

Given that all rock arches have limited lifespans and the Trump administration recently reduced protected areas in Bears Ears and Grand-Escalante National Monuments by approximately 2 million acres (809,3715 hectares), Moore's team has embarked on creating a digital archive to preserve these natural formations in case of commercial development impacts. This archive features over 115 arches, complete with photographs, interactive 3-D models, and audio recordings for select arches.