Mid-Tertiary ignimbrite flare-up

The Mid-Tertiary ignimbrite flare-up,[lower-alpha 1] was a dramatic period of volcanic eruptions in mid-Cenozoic time, approximately 25–40 million years ago, centered in the western United States.[2] These eruptions are seen today as deposits of ignimbrite, the pyroclastic material that was laid down from these eruptions.

Mid-Tertiary ignimbrite flare-up
The Fish Canyon Tuff ignimbrite
VolcanoMultiple cumulative events
Date25-40 million years ago
LocationWestern United States
ImpactDeposited vast swatches of ignimbrite across the western United States

Overview

There were numerous eruptions within the flare-up. The total volume includes 5x105 km3 of ash flow tuff and 5x106 km3 of intermediate and silicic lava.[3] This amount is on par for some of the largest non-explosive volcanic provinces (see World's largest eruptions). For reference, the 1980 eruption of Mt. St. Helens was about 1 km3. The largest eruption on the flare-up, and also the largest explosive eruption ever known, was the Fish Canyon tuff in southwest Colorado. Its volume alone is 5,000 km3. The three primary volcanic centers of the flare-up are the Central Nevada volcanic field of central Nevada, Indian Peak volcanic field of eastern Nevada/western Utah, and the San Juan volcanic field in Colorado.

Cause

The primary tectonic driving force behind this explosive volcanic activity is slab rollback.[4] During the Laramide orogeny, the subducting Farallon Plate subducted at a very shallow angle. When this stopped, the mantle wedge was opened up, and the result was the flare-up. The specifics of this opening, including possible slab rollback,[5] slab windows,[6] or buckling of the plate,[7] can explain specific volcanic trends within the flare-up.

See also

Notes
  1. This designation has as a part of it a term, 'Tertiary', that is now discouraged as a formal geochronological unit by the International Commission on Stratigraphy.[1]

References
  1. Ogg, James G.; Gradstein, F. M; Gradstein, Felix M. (2004). A geologic time scale 2004. Cambridge, UK: Cambridge University Press. ISBN 0-521-78142-6.
  2. Cannon, Eric. "The Mid-Tertiary ignimbrite flare-up". Archived from the original on 16 July 2012. Retrieved 14 August 2010.
  3. Cannon, Eric. "1. Introduction: The Mid-Tertiary ignimbrite flare-up". Archived from the original on 25 September 2012. Retrieved 14 August 2010.
  4. Cannon, Eric. "5. Tectonics: The Mid-Tertiary ignimbrite flare-up". Archived from the original on 4 March 2016. Retrieved 14 August 2010.
  5. Best, Myron G.; Christiansen, Eric H.; de Silva, Shanaka; Lipman, Peter W. (August 2016). "Slab-rollback ignimbrite flareups in the southern Great Basin and other Cenozoic American arcs: A distinct style of arc volcanism". Geosphere. 12 (4): 1097–1135. Bibcode:2016Geosp..12.1097B. doi:10.1130/GES01285.1.
  6. Breitsprecher, K.; Thorkelson, D.J.; Groome, W.G.; Dostal, J. (1 April 2003). "Geochemical confirmation of the Kula-Farallon slab window beneath the Pacific Northwest in Eocene time". Geology. 31 (4): 351–354. Bibcode:2003Geo....31..351B. doi:10.1130/0091-7613(2003)031<0351:GCOTKF>2.0.CO;2.
  7. Humphreys, Eugene D. (1 November 1995). "Post-Laramide removal of the Farallon slab, western United States". Geology. 23 (11): 987–990. Bibcode:1995Geo....23..987H. doi:10.1130/0091-7613(1995)023<0987:PLROTF>2.3.CO;2.
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