Colorado College students owe the beauty of Colorado’s mountains to the geological changes in the Earth’s crust during Proterozoic and Phanerozoic eons. In due homage, CC Professor Paul Myrow and Jitao Chen, his assistant from the Nanjing Institute of Geology and Paleontology, have been dedicating their research to the ancient earthquakes that helped form the structure of the Grizzly Creek Shear Zone at Glenwood Canyon, CO.
They published their research in the geology journal Sedimentology, in an article titled “Estimates of Large Magnitude Late Cambrian Earthquakes from Seismogenic Soft-Sediment Deformation Structures: Central Rocky Mountains,” but Myrow is currently in the process of writing a paper about some of Colorado’s largest earthquakes from the distant past.
According to Myrow, a popular hiking trail in the central Rockies known as the Grizzly Creek Shear zone “is a fault zone, a plane of weakness in the crust that moved in the Proterozoic and then several time in the Phanerozoic.” Over the timespan of oxygen beginning to accumulate in the Earth’s atmosphere to the appearance of modern fauna, this zone was reactivated several times. Around 60 percent of the modern continental crust formed during the Proterozoic
and Phanerozoic geological eras, marked by the steady formation of Pangaea, the mono-continent of the ancient Earth. During those eons, a shallow sea covered the Western U.S.
These ancient earthquakes could be some of the largest earthquakes to ever occur in the Central Rockies. As said on the Colorado College website, based on the size, shape, and distribution of the rock debris in the area, Myrow and Chen can estimate that the earthquakes were an X or greater on the Mercalli Index, at a 7.0 magnitude or greater. In comparison, U. S. News reported a 6.0 magnitude for the recent earthquake in Napa, California, that injured 120 people.
Of course, the current discussion of earthquakes in Colorado is very different from Myrow’s work. A report by Trevor Hughes for USA Today on Aug. 20 comments on how the steady rise of earthquakes’ magnitude in Colorado since 2009 is likely linked to Colorado’s recent increase in petroleum production. Recently, a number of uncharacteristic earthquakes were recorded near a well being pumped with the drillings’ wastewater. Many residents blame the earthquakes on the drilling companies’ economic choice to not clean or properly dispose of the polluted water from injection wells.
Though still very rare in Colorado, stress over earthquakes seems to be more prevalent. The recent increase in earthquake incidences has resulted in more frequent—and possibly more exaggerated—news coverage. In fact, when 9NEWS contacted Myrow, the reporter assumed that Myrow’s research was about current earthquakes.
“An earthquake took place in California recently,” Myrow said, clearing the confusion. “This is completely unrelated.”
The actual possibility of an earthquake occurring in Colorado like the ancient ones at Grizzly Creek is very unlikely. 9NEWS recently helped make that more clear with a story on Aug. 25, which explained the unlikelihood that Colorado will see an earthquake with a higher magnitude than 5 or 6. The geological destruction that created the Rockies won’t be taking them away from us anytime soon.