Yellowstone hotspot had much larger eruptions than thought

Researchers have discovered that the large super-eruptions that took place at a Yellowstone hotspot in Idaho about 8 to 12 million years ago were even more “super” than previous studies had suggested they were.

A team of researchers led by Dr. Thomas Knott of the University of Leicester headed to Yellowstone to look further into these ancient super-eruptions. According to their findings, the number of eruptions believed to have originated from Idaho’s central Snake River Plain was less than expected. Still, the 12 super-eruptions that took place in ancient times may have been “significant larger” than researchers had originally theorized.

Knott’s team used a “multi-technique approach,” using paleomagnetic data, radio-isotopic dating, and analysis of whole-rock and mineral chemistries, to track the fingerprints of individual eruption deposits, and correlate these tracks over regions of about 1,000 square kilometers. That allowed them to significantly reduce the eruption count in that region.

One of the newly-discovered super-eruptions was the Castleford Crossing Eruption, which happened about 8.1 million years ago. Its eruption volume may have exceeded 1,900 km3, while its volcanic sheet spans more than 14,000 square kilometers, and is over 1.3 kilometers thick in the caldera. This eruption was substantially more destructive than once thought, and may be as powerful as the better-known, previously-documented super-eruptions at Yellowstone.

“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,” Knott said in a statement. He added that the size and magnitude of the Castleford Crossing Eruption is “as large, if not larger than better known eruptions at Yellowstone,” and that it is merely the first of a series of newly-discovered super-eruptions that happened between 8 to 12 million years ago.