Is the Yellowstone Supervolcano part of a volcanic system that was much larger and violent between eight and 12 million years ago? That is the latest question following the discovery of 12 giant super-eruptions around the Snake River Plain.
"While it is well-know that Yellowstone has erupted catastrophically in recent times, perhaps less widely appreciated is that these were just the latest in a protracted history of numerous catastrophic super-eruptions that have burned a track along the Snake River eastwards from Oregon to Yellowstone from 16 Ma to present," explained Tom Knott, one of the study researchers from the University of Leicester's Department of Geology's Volcanology Group.
Knott and colleagues Mike Branney and Marc Reichow led an international team of researchers in studying eruption deposits that are believed to have originated from the central Snake River Plain - a prominent depression stretching 400 miles across southern Idaho.
Based on whole-rock and mineral chemistries, palaeomagnetic data, and radio-isotopic dating, researchers identified 12 giant super-eruptions thought to have occurred between 8 and 12 million years ago. In theory, these eruptions could be larger than the colossal eruptions known to have taken place at Yellowstone.
While the recent study reduces the number of volcanic eruptions thought to have originated from the central Snake River Plain by more than half, researchers suggest the 12 recorded giant eruptions were likely "significantly larger" than previously thought and may even rival those better known at Yellowstone.
"The size and magnitude of this newly defined eruption is as large, if not larger, than better known eruptions at Yellowstone, and it is just the first in an emerging record of newly discovered super-eruptions during a period of intense magmatic activity between 8 and 12 million years ago," Knott added.
For instance, one of the super-eruptions, defined as the Castleford Crossing eruption, occurred about 8.1 million years ago and is estimated to far surpass an eruption volume of 1,900 cubic kilometers. This volcanic eruption alone blankets an area over 14,000 square kilometers in southern Idaho and is more than 1.3 kilometers thick in the caldera of the super-volcano.
Furthermore, researchers revealed that intense hotspot magmatism likely caused major crustal subsidence, forming what is now the 100-kilometer-wide Snake River Basin.
The study also involved the work of researchers from the University of California, Santa Cruz, the University of Copenhagen and Idaho State University. Their findings were recently published in the Geological Society of America Bulletin.
