A thorough examination of tiny crystals of zircon, a mineral found in rhyolites, an igneous rock, from the Snake River Plain has solidified evidence for a new way of looking at the life cycle of super-volcanic eruptions in the long track of the Yellowstone hotspot, say University of Oregon scientists.

The pattern emerging from new and previous research completed in the last five years under a National Science Foundation career award, said UO geologist Ilya Bindeman, is that another super-eruption from the still-alive Yellowstone volcanic field is less likely for the next few million years than previously thought (see related story, "Not in a million years, says Oregon geologist about Yellowstone eruption"). The last eruption 640,000 years ago created the Yellowstone Caldera and the Lava Creek Tuff in what is now Yellowstone National Park.

The Yellowstone hotspot creates a conveyor belt style of volcanism because of the southwest migration of the North American plate at 2-4 centimeters (about .8 to 1.6 inches) annually over the last 16 million years of volcanism. Due to the movement of the North American plate, the plume interaction with the crust leaves footprints in the form of caldera clusters, in what is now the Snake River Plain, Bindeman said.

The Picabo volcanic field of southern Idaho, described in a new paper by a six-member team, was active between 10.4 and 6.6 million years ago and experienced at least three, and maybe as many as six, violent caldera-forming eruptions. The field has been difficult to assess, said lead author Dana Drew, a UO graduate student, because the calderas have been buried by as much as two kilometers of basalt since its eruption cycle died.

The work at Picabo is detailed in a paper online ahead of publication in the journal, “Earth and Planetary Science Letters.”

- from a story by Jim Barlow, UO Office of Strategic Communications