An ancient piece of oceanic crust that lodged itself beneath the North American continent created the Yellowstone Caldera and other volcanoes in the hotspot track, new research shows.

Experts at the Virginia Tech College of Sciences say that the Yellowstone super-volcano was created by an enormous plate that moved when the continents started to split some 175 millions years ago.

The plate wedged itself under North America, broke off into tiny pieces, and set hot materials up to the surface of the Earth. This led to the creation of the super-volcano and the Yellowstone hotspots track that runs along Oregon, Idaho, and Wyoming.

Yellowstone Super-Volcano

The Yellowstone super-volcano is a vast expanse of a volcano that covers practically the entire Yellowstone National Park. A super-volcano is a volcano that has erupted at magnitude 8, the highest on the Volcanic Explosivity Index.

The dormant Yellowstone has erupted only three times in the last 2.1 million years, the last one taking place 640,000 years ago at Lava Creek. This led to the creation of the Yellowstone Caldera, a giant crater over 1,500 square miles in area that formed when the volcano collapsed in the catastrophic eruption.

If the super-volcano erupts again, it will send nuclear winds throughout the world, emit a cloud of ash that will darken the sky for days, and devastate two-thirds of the United States.

Oceanic Crust Subduction  

The new paper published in the journal Natural Geoscience runs counter to the prevailing theory of how the Yellowstone super-volcano came into being.

For years, experts have believed that the super-volcano was created by a plume of magma rising from the Earth's core and passing through rifts in the crust to create the super-volcano.

However, lead researcher Ying Zhou, theoretical seismologist at Virginia Tech's Department of Geosciences, says scientists have not yet found evidence of a plume of hot materials underneath Yellowstone.

Instead, the subterranean images taken by Zhou and her team show evidence of an enormous oceanic plate that subducted the Western United States 30 million years ago.

Called the Farallon Plate, it broke into pieces and melted in the mantle. This sent magma to the crust that has been causing volcanic eruptions for the past 16 million years.

Underground Images Show Anomalous Structure  

Working at the National Science Foundation's underground USArray observatory, the team was able to create images of underground structures with the help of seismic waves generated by the movement of tectonic plates. This is called diffraction tomography.

Using this new technique, the researchers spotted an anomalous subterranean structure found 250 to 400 miles that follows the trail of the hotspots track.

This suggests that the Farallon Plate sank deep into the mantle and pushed magma upward to form Yellowstone. The hotspots track has been moving northwest ever since, says Zhou.

"The process started at the Oregon-Idaho border about 16 million years ago and propagated northwestward, forming a line of volcanoes that are progressively younger as they stretched northwest to present-day Wyoming," she says.

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