Today, Colorado's mountainous interior experiences four distinct seasons thanks to a temperate climate. However, 325 million years ago and roughly 100 million years before the existence of the first dinosaurs, a temperate climate was not the case. In the later part of the Paleozoic Era, the area of modern day Minturn was a tropical region, covered in shallow seas teaming with marine organisms such as tube worms, sea lilies and corals.
Photo credit: cozephyr on Flickriver.com
As millions of these organisms died and settled on the seafloor, they began forming the limestone layers of the Minturn cliffs. Fossils of corals found in the sediment of Lionshead Rock has led geologists to believe the rock formation was once part of an ancient coral reef. In addition to these limestone layers, sediments of the long eroded ancestral Rocky Mountains make up Lionshead Rock and surrounding cliffs. Formed from these deposits of preexisting rock and dead organisms compressed over time, Lionshead Rock is a prime example of a sedimentary rock. What goes up though, must come down and millions of years of erosion of these cliffs have shaped Lionshead Rock as we know and love it today. Although most of this erosion has been small and incremental over millennia, in 2014 Lionshead Rock changed suddenly and dramatically.
The falling of Lionshead Rock- Well, part of it
Residents in Minturn heard a loud rumbling around 8 p.m. on March 4th, 2014. Some residents described it as a helicopter while others thought it was a bomb, but in reality, it was a large piece of Lionshead Rock breaking off from the south side of the rock face. The boulder rolled down the mountain, breaking into two pieces on the way down. The boulders hit the railroad tracks, just missing the buildings located nearby. It is believed that the boulder cracked off due to the freeze-thaw cycle that commonly occurs each spring in Colorado. The freeze-thaw cycle is a process in which water melts and flows into the crevices of the rock, before refreezing and expanding. This happens over and over, slowly widening these fractures in the rock. In the case of Lionshead Rock, the freeze-thaw cycle eventually widened a crack so much that part of the rock broke free.
Kelly Luebbering is a winter naturalist at Walking Mountains Science Center who is experiencing her first winter in Colorado. She has been enjoying snowshoeing and learning how to ski.
Chronic, H. (1996). Roadside geology of Colorado. Missoula, MT: Mountain Pr. Publ.
Gibbons, K. (2014, March 08). Large chunk of Lionshead rock breaks off. Retrieved January 07, 2021, from https://www.denverpost.com/2014/03/08/large-chunk-of-lionshead-rock-breaks-off/
Wong, M. (2014, March 07). Minturn icon Lionshead Rock to be missed, locals say. Retrieved January 07, 2021, from https://www.vaildaily.com/news/minturn-icon-lionshead-rock-to-be-missed-locals-say/