Lava formations in eastern Oregon linked to rip in giant slab of Earth

Feb 15, 2012
Image: Hawaii Volcano Observatory (DAS)

Like a stream of air shooting out of an airplane's broken window to relieve cabin pressure, scientists at Scripps Institution of Oceanography at UC San Diego say lava formations in eastern Oregon are the result of an outpouring of magma forced out of a breach in a massive slab of Earth. Their new mechanism explaining how such a large volume of magma was generated is published in the Feb. 16 issue of the journal Nature.

For years scientists who study the processes underlying the planet's shifting and how they shape the planet have debated the origins of sudden, massive eruptions of lava at the planet's surface. In several locations around the world, such "flood basalts" are marked by immense formations of . A famous example is India's Deccan flood basalt, a formation widely viewed as related to the demise of the dinosaurs 65 million years ago.

Such eruptions are thought to typically occur when the head of a , a mushroom-shaped upwelling of hot rock rising from deep within the earth's interior, reaches the surface. Now Scripps postdoctoral researcher Lijun Liu and geophysics professor Dave Stegman have proposed an alternative origin for the of Oregon's Columbia River flood basalt.

Liu and Stegman argue that around 17 million years ago the tectonic plate that was subducting underneath the western United States began ripping apart, leading to massive outpourings of magma. Their proposed model describes a dynamic rupture lasting two million years—a quick eruption in geological terms— across the so-called Farallon slab, where the rupture spread across 900 kilometers (559 miles) along eastern Oregon and northern Nevada.

"Only with a break of this scale inside the down-going slab can we reach the present day geometry of mantle we see in the area," said Liu, "and geochemical evidence from the lavas can also be explained by our model."

"When the slab is first opened there's a little tear, but because of the high pressure underneath, the material is able to force its way through the hole. It's like in the movies when a window breaks in an airplane that is at high altitude—since the cabin is at higher pressure, everything gets sucked out the window," said Stegman, an assistant professor with Scripps' Cecil H. and Ida M. Green Institute of Geophysics and Planetary Physics.

Liu and Stegman came upon their new mechanism by attempting to describe how the complicated structure of the earth's mantle under the western U.S. developed during the past 40 million years. The final state of their model's time-evolution matches the present day structure as imaged by the USArray, the National Science Foundation's transportable seismic network of 400 sensor stations leapfrogging across the United States.

"This paper highlights the importance of interdisciplinary efforts in Earth sciences," Liu added.

Explore further: NASA sees Genevieve squeezed between 3 tropical systems

Related Stories

New force driving Earth's tectonic plates discovered

Jul 06, 2011

Bringing fresh insight into long-standing debates about how powerful geological forces shape the planet, from earthquake ruptures to mountain formations, scientists at Scripps Institution of Oceanography at ...

Reservoirs of ancient lava shaped Earth

Jul 27, 2011

Geological history has periodically featured giant lava eruptions that coat large swaths of land or ocean floor with basaltic lava, which hardens into rock formations called flood basalt. New research from Matthew Jackson ...

New insights into volcanic activity on the ocean floor

Jun 16, 2010

New research reveals that when two parts of the Earth's crust break apart, this does not always cause massive volcanic eruptions. The study, published today in the journal Nature, explains why some parts ...

Recommended for you

Cordilleran terrane collage

3 hours ago

In the August 2014 issue of Lithosphere, Steve Israel of the Yukon Geological Survey and colleagues provide conclusions regarding the North American Cordillera that they say "are provocative in that they b ...

NASA sees Tropical Storm Halong's 'best side'

5 hours ago

NASA satellite data showed Tropical Storm Halong's "best side" or most powerful side was east of its center. That's where the coldest cloud top temperatures and strongest thunderstorms appeared on satellite ...

User comments : 0