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Mid-Tertiary ignimbrite flare-up

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Title: Mid-Tertiary ignimbrite flare-up  
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Mid-Tertiary ignimbrite flare-up

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

Overview

There are countless eruptions within the flare-up; the total volume includes 5x105 km3 of ash flow tuff and 5x106 km3 of intermediate and silicic lava.[2] 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 roll back.[3] 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 windows or buckling of the plate, can explain specific volcanic trends within the flare-up.

See also

References

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