San Juan volcanic field

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San Juan volcanic field
San Juan volcanic field is located in Colorado
San Juan volcanic field
San Juan volcanic field
Location in Colorado
Location Colorado, United States
Coordinates 37°53′36″N 106°46′28″W / 37.89333°N 106.77444°W / 37.89333; -106.77444Coordinates: 37°53′36″N 106°46′28″W / 37.89333°N 106.77444°W / 37.89333; -106.77444
Type Volcanic field

The San Juan volcanic field, in southwestern Colorado, contains two phases of volcanism.

The earlier volcanism is Oligocene in age, and consists of largely intermediate composition lavas and breccias. A few ash flow tuffs also constitute this phase of volcanism. It probably was related to subduction along the western margin of North America.

The later volcanism is MiocenePliocene in age, and is basaltic in composition. It is best interpreted as a partial melt of the lower crust that was erupted onto the surface.[1]

Notable calderas[edit]

Name Elevation Coordinates Age
Cochetopa Caldera - 38°12′N 106°45′W / 38.2°N 106.75°W / 38.2; -106.75[2]
Nelson Mountain Caldera - 37°58′N 106°56′W / 37.96°N 106.93°W / 37.96; -106.93[2]
Bachelor Caldera - 37°49′03″N 106°54′46″W / 37.817378°N 106.912766°W / 37.817378; -106.912766[2]
Creede Caldera - 37°45′34″N 106°56′20″W / 37.759316°N 106.938858°W / 37.759316; -106.938858[2]
Lake City calderas - 38°01′31″N 107°23′04″W / 38.025377°N 107.384491°W / 38.025377; -107.384491[1]
Platoro calderas - 37°21′08″N 106°31′52″W / 37.352147°N 106.530991°W / 37.352147; -106.530991[1]

See also[edit]


  1. ^ a b c Lipman, P.W.; Doe, B.R.; Hedge, C.E.; Steven, T.A. (1978). "Petrologic evolution of the San Juan volcanic field, southwestern Colorado: Pb and Sr isotope evidence". Geological Society of America Bulletin 89: 59–82. doi:10.1130/0016-7606(1978)89<59:PEOTSJ>2.0.CO;2. ISSN 0016-7606. 
  2. ^ a b c d e Robinson, Joel E.; Dillon R. Dutton; David W. Ramsey; Peter W. Lipman; Tracey J. Felger (2006). Geologic Map of the Central San Juan Caldera Cluster, Southwestern Colorado: Geologic Investigations Series. I-2799. U.S. Geological Survey. Retrieved 2010-05-03.