John Wolff looks at the microprobe computer screen to view an analysis of a rock
sample. (Photos by Becky Phillips, WSU Today)
 
 
Nick Foit holding a garnet crystal.
The geologists had warned them — but people were still caught off guard when Mount St. Helens erupted in 1980. The ferocity of that explosion went beyond all predictions and killed 57 people. Today, in a quiet laboratory on the WSU Pullman campus, John Wolff is developing an early warning system to monitor volcanoes capable of spewing a thousand times more rock and ash than Mount St. Helens.
 
Eruption of these supervolcanoes — like the 47-mile-long Yellowstone caldera — lies outside the realm of recorded human experience and could have devastating regional and global impacts, such as climate change and extinction of species.
 
“It has been hypothesized that the last such eruption — which occurred in Indonesia about 75,000 years ago — almost killed off the human race,” said Wolff, professor in the School of Earth and Environmental Sciences (SEES) and director of the WSU GeoAnalytical Laboratory.
 
With the recent swarm of earthquakes at Yellowstone National Park, his concern is not just academic.
 
“It’s quite certain one of these things will happen in the future — but we don’t know if it will be 30 years or 10,000,” he said. “From the geological record, we know there have been tens of thousands of these events over time. The question is … how will we see it coming?”
 
Microprobe power
Wolff’s efforts to answer that question recently were boosted by a grant from the National Science Foundation funding his study of the Valles caldera in New Mexico — one of three supervolcanoes in the western U.S. (The third one lies in Long Valley in eastern California.)
 
Coincidentally, WSU also was awarded a $600,000 NSF grant to purchase a JEOL 8500F microprobe, which allows for unprecedented analysis and imaging of volcanic ash crystals down to the submicron scale.
 
“It is only the third such instrument in the U.S. — and our probe is the only one used to support commercial enterprise,” said Franklin (Nick) Foit, principal investigator on the grant and professor in SEES. As a mineralogical crystallographer, Foit uses the microprobe to study mineral chemistry and date archeological sites for his university research as well as for more than 100 private consultants.
 
The microprobe also supports the research of nearly two thirds of the school’s graduate students. See ONLINE @ www.sees.wsu.edu/Geolab/index.html.
 

Compositional zoning shows up
as light and dark bands in this
rock sample.

The grenade pin
For Wolff, the microprobe provides key information toward reconstructing events that lead up to a supereruption — and from there determining how those events can be detected on the earth’s surface.

 
“There may be a particular pattern of seismic activity that can predict an eruption, for example,” he said.
 
Wolff likened this to the pin being pulled out of a grenade.
 
“We want to be able to hear the ‘pin’ being pulled out in time to escape the explosion.” The pin in this case is thought to be some type of disturbance such as the intrusion of new magma into the caldera. The magma heats and agitates the volcanic system causing characteristic changes in rocks and crystals.
 
Using the microprobe, Wolff and his team are zeroing in on certain crystals — called phenocrysts — that lie within the finer-grained ash and pumice from past eruptions. These crystals — which vary their chemical composition in response to magma changes — handily preserve a record of magma activity prior to massive eruptions. The chemical variations show up in the rock as distinct bands referred to as compositional zoning.
 

A calcium x-ray map of a rock
sample.

Zone boundaries
The new microprobe — with its 100-nanometer resolution — is able to image the boundaries between these zones to a level of detail previously unattainable.

 
In a study completed last fall, Wolff analyzed quartz from the Valles caldera and formulated a model showing that the crystal profile in that rock could have existed no longer than 20 years at 750 degrees C or five years at 800 degrees C prior to an eruption. Previous scientific studies could only pinpoint eruptions to within about 100 years.
 
“We know this is a general feature of these (supervolcanic) systems,” said Wolff. “Pumice and ash taken from the Long Valley supervolcano showed the same series of zone boundaries – indicating that the exact same sequence of events took place.”
 
A thin section of rock that can be
examined in the microprobe.
(Photos by Becky Phillips, WSU
Today) 

Though it is only preliminary data, Wolff feels that the formation of zone boundaries may be the elusive “grenade pin.” Once those changes in magma can be detected on the earth’s surface, he believes society could have enough warning to deal with a supereruption.

 
“If we can say it will happen 20 or 30 years from now, we could put a lot of resources into it… sort of like the Manhattan Project.”