Title

The Ignimbrite Storm: Causes and Significance

Date

6-1-2017 2:00 PM

End Time

1-6-2017 3:00 PM

Location

RWEC 201

Department

Earth Science

Session Chair

Jeffrey Templeton

Session Title

Earth Science Senior Seminar: Understanding the Tectonic Development and Framework of western North America

Faculty Sponsor(s)

Jeffrey Templeton

Presentation Type

Presentation

Abstract

Between 25 and 40 million years ago, western North America was dominated by explosive volcanism, during an event referred to as the ‘ignimbrite flare-up’. Caldera complexes in the Basin and Range erupted huge volumes of silicic magma, depositing pyroclastic debris thousands of kilometers away. The caldera-forming eruptions began in northern Nevada and migrated to the southwest over 15-20 m.y. Another sequence of calderas swept across New Mexico towards the WNW with additional calderas in Colorado. What is the significance of the ‘ignimbrite flare-up’, and what does it imply about tectonic activity during this time? Two competing models have been proposed to explain the age-progressive trends in explosive volcanism. One model suggests that the subducted Farallon Plate buckled allowing underlying asthenosphere to move upward through fractures formed by the compressional forces in the broken slab. The second model involves slab roll back in which buoyant asthenosphere was pushed above the Farallon Plate as the slab was bent to higher angles. Evaluating the merits of each provides a framework for understanding how tectonics can influence caldera-forming eruptions.

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Jun 1st, 2:00 PM Jun 1st, 3:00 PM

The Ignimbrite Storm: Causes and Significance

RWEC 201

Between 25 and 40 million years ago, western North America was dominated by explosive volcanism, during an event referred to as the ‘ignimbrite flare-up’. Caldera complexes in the Basin and Range erupted huge volumes of silicic magma, depositing pyroclastic debris thousands of kilometers away. The caldera-forming eruptions began in northern Nevada and migrated to the southwest over 15-20 m.y. Another sequence of calderas swept across New Mexico towards the WNW with additional calderas in Colorado. What is the significance of the ‘ignimbrite flare-up’, and what does it imply about tectonic activity during this time? Two competing models have been proposed to explain the age-progressive trends in explosive volcanism. One model suggests that the subducted Farallon Plate buckled allowing underlying asthenosphere to move upward through fractures formed by the compressional forces in the broken slab. The second model involves slab roll back in which buoyant asthenosphere was pushed above the Farallon Plate as the slab was bent to higher angles. Evaluating the merits of each provides a framework for understanding how tectonics can influence caldera-forming eruptions.