Contrast of Opinions Concerning the Formation of the Black Canyon

Scientists postulate the complex physical processes coupled with immense amounts of time that work together to form phenomena like the Black Canyon of the Gunnison, and often disagree. I’m going to contrast the explanation given on the USGS website with the explanation of local Geologist, Shawn La Bounty.

Black Canyon of the Gunnison
Photo Credit: Nefratiri Weeks

The USGS explanation states that about 2,000 million years ago (mya), the entire area was covered with an ancient ocean.

Gunnison River
Photo Credit: Nefratiri Weeks

In the late Cretaceous Period, the Laramide orogeny took place – tectonic plates, “jockeying for position” caused the beginning of the building of the Rocky Mountains (Thornberry-Ehrlich, 2005, p. 20). Also during this time, a local event took place, called the Gunnison Uplift, which raised the anticline where the Black Canyon is located.

About 25 mya, the Tertiary period brought volcanic eruptions from surrounding mountain ranges – the West Elks and San Juans.

This volcanic activity resulted in pyroclastic flows that covered the area with rock and ash. Coupled with snowfall, this helped form the headwaters of the Gunnison River.

Around 2-3 mya, another “broad uplift initiated a period of active erosion” which is when the Canyon was formed (ibid., p. 20). The Gunnison River began flowing across the plateau of the soft ash sediment.

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References:

Thronberry-Ehrlich, T. 2005. Black Canyon of the Gunnison National Park & Curecanti National Recreation Area Geologic Resource Evaluation Report. Natural Resource Report NPS/NRPC/GRD/NRR--2005/001. National Park Service, Denver, Colorado. http://www.nature.nps.gov/geology/inventory/publications/reports/blca_cure_gre_rpt_view.pdf. Retrieved October 18, 2010.

USGS: Geological Survey Bulletin 1191. Black Canyon of the Gunnison Today and Yesterday: Rock Formations - Why the Black Canyon Crosses the Gunnison Uplift. http://www.nps.gov/history/history/online_books/geology/publications/bul/1191/sec3.htm. Retrieved November 29, 2010.