As part of the research, Geimer has led an effort to collect 3-D imagery of the rock structures to precisely measure the rocks' dimensions — helping the researchers learn even more about what makes these rocks rumble.

"As of just a few years ago there were almost no measurements of the kind in existence," Moore said, "so every feature we measure is something new."

Climbing assistants

Placing a seismometer at the top of Castleton Tower required someone ascending to the top to install and retrieve the equipment. Fortunately, two professional climbers on a seasonal break from their employment offered their skills and equipment.

To get the needed data, the climbers trekked to the base of the tower and placed a seismometer to serve as a reference. Geimer says that on the day of the experiment, in March 2018, the weather was good and the climbing route up the popular tower was filled with a consistent stream of climbers.

"I can imagine both anxiety and excitement levels spiked when the team walked away from the reference and began the climb to the top," Geimer said, "knowing that it would be hours before returning safely to the base and verifying a successful measurement."