Thirtynine Mile volcanic area

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Coordinates: 38°49′56″N 105°33′16″W / 38.8322°N 105.5544°W / 38.8322; -105.5544

The Thirtynine Mile volcanic area, part of the larger Central Colorado volcanic field, is an extinct volcanic area located in Park and Teller counties, Colorado, northwest of Cripple Creek and southeast of South Park.[1] The area was the site of significant volcanism in the Paleogene Period about 35 million years ago. Ashfall and lahars (mudflows) from the volcanoes created the conditions for fossilization at what is now Florissant Fossil Beds National Monument.

The area is named for Thirtynine Mile Mountain, a local peak that is composed of volcanic rocks from the field. The area also contains the Guffey volcanic center.[2]


  1. ^ McIntosh, William C.; Chapin, Charles E. (2004). Geochronology of the central Colorado volcanic field (PDF). New Mexico Bureau of Geology and Mineral Resources, Bulletin 160. Retrieved 2010-03-31. 
  2. ^ Wobus, Reinhard A.; et al. (July 1990). "Geochemistry of high-potassium rocks from the mid-Tertiary Guffey volcanic center, Thirtynine Mile volcanic field, central Colorado". Geology. 17: 642–645. Retrieved 2016-03-21.