San Diego State University geology lecturer Victor Camp has spent a lifetime studying volcanic
eruptions all over the world, starting in Saudi Arabia, then Iran and, eventually, the Pacific
Northwest. Mantle plumes—upwellings of abnormally hot rock within Earth’s middle layer—that
feed the largest of these eruptions fascinate Camp because of their massive size and potential effect
on our environment.
Over the past few years, he has discovered that the mantle source rock that rises from beneath
Yellowstone National Park to feed its periodic supereruptions also spreads west all the way out
to Northern California and Oregon.
On its westward journey, it acts as the catalyst for fairly young—meaning less than two million
years old— volcanic eruptions at places such as Craters of the Moon National Monument and
Preserve in Idaho, before reaching Medicine Lake Volcano in northeastern California.
Many miles deep beneath Earth’s surface, the mantle rock spreads laterally through narrow flowline
channels for more than 500 miles, bifurcating twice: once as it leaves Yellowstone and again as
it reaches the California-Oregon border. These lines end at Medicine Lake, an active volcano near
Mount Shasta, and at Newberry Volcano, an active volcano about 20 miles south of Bend, Oregon.
This discovery, published in the journal Geology in May 2019, is significant because it reveals how
mantle plumes similar to the one beneath Yellowstone behave as they feed the majority of the
world’s largest volcanic eruptions of basaltic lava, including those in Hawaii.
“Since the plume is not controlled by plate tectonics, it can rise and emerge anywhere on Earth,
depending on where it manages to break through the earth’s surface,” Camp said. “So, knowing
this will help us understand supereruptions that have occurred before, and those that will occur
in the future.”
When the Yellowstone plume first reached the base level of the North American tectonic plate,
it was blocked by the cold plate’s rigidity. At the depth of about 62 miles, the plume began to
decompress and melt, while spreading laterally to the west.
The mantle rock under Yellowstone today originated at the bottom of the mantle geographically
centered near what is now San Diego and took millions of years to move east before tracking
back west.
Camp sourced seismic tomography images, similar to X-rays and CT scans (computerized tomography
scans), that show how the mantle plume ascended. He also analyzed field data and published
chemistry and age data on volcanic rocks at the surface to demonstrate its westward flow.