Published: Oct. 12, 2022

A new exhibit on the first-floor of the Earth Sciences & Map Library demystifies the process of how to use laboratory dating methods to determine the absolute age of Earth materials.

“How to Date a Rock” is a geochronological display curated by Barra Peak, a fourth-year PhD student in the Department of Geological Sciences at CU Boulder. The exhibit is a public outreach extension of her investigation into a geological feature called “the great unconformity,” or the phenomenon where two different kinds of rocks come into contact. 

“This feature has been kind of an enigma of geological understanding for a long time,” Peak explains. “People have noticed that there’s clearly a distinction between rocks that are below the contact and the rocks above, but it’s unclear how it formed, on what time scales and if the erosion that occurred to create the event contributed to things like evolution of complex life or massive climate changes in Earth’s past.” 

Visible in geological regions throughout North America but featured prominently in the western U.S., the Great Unconformity can be found while hiking in areas like the Grand Canyon National Park in Arizona or Flagstaff Mountain in Boulder, Colorado. Those who visit the exhibit will find graphic panels explaining the measurement of geological time with a display case that uses samples to distill the rock dating process in 10 easy-to-follow steps.

Naomi Heiser, map curator and metadata projects manager, oversaw the installation of “How to Date a Rock”, in the Earth Sciences & Map Library. She says that electing to host Peak’s exhibit was a no-brainer. 

“This is an exhibit done by a geosciences PhD student who is using our library resources to conduct educational outreach,” Heiser said. “We have a space that’s available for students in the geosciences and other fields to use and exhibit, but this is the first exhibit we have hosted in this library location that includes actual geological specimens and research materials.” 

Peak says that she found the perfect home for “How to Date a Rock” in the Earth Sciences & Map Library. 

“Because it is on the first floor of the main study area, I think in terms of reaching people that it’s in the best possible location because lots of students and other people use that space,” Peak added. “It’s just a really nice place to study and do work.” 

Rebecca Flowers is a geological sciences professor at CU Boulder and principal investigator on the National Science Foundation grant Peak received to study the age and origin of Great Unconformity. She says that this geological phenomenon is an easy entry-point for aspirational scientists, and that answering this specific scientific question has been a collective endeavor. 

“This exhibit is part of our educational effort to communicate the importance of timing constraints for addressing fundamental questions in Earth system science, including those related to climatic, environmental, landscape and solid Earth change,” Flowers said. 

Stop by the Earth Sciences & Map Library any time between now and the end of the school year during open hours to learn “How to Date a Rock.”