I posted on the bulging at
Yellowstone last year and we now have this item from theNational Geographic. One finds that theprocess is largely benign and likely to remain so. Certainly there is no mountain building goingon.
The sheer of the super volcano isstaggering and well worth celebrating. Of course, I would love to see it all tapped for geothermal energy, evenif that meant burying the facilities. The yield would be high and the capacity would be huge. However the designation of national park sharplycurtails such efforts although it actually should not.
Our problem is that there is abelief that all development requires an unlimited surface right which is nottrue and also bone stupid. The oilindustry today comes, extracts and cleans up and leaves a land that is swiftlyreclaimed by nature.
Geothermal works on a closedcircuit basis and placing the surface component underground or part of ageneral park facility is not difficult. Everything else (particularly power lines) can be buried and should beanyway.
Some places saw the ground rise by ten inches, experts report.
Steam rises from Castle Geyser in
(file photo). Yellowstone National Park
Photograph by Mark Thiessen, National Geographic
Published January 19, 2011
Yellowstone National Park's supervolcanojust took a deep "breath," causing miles of ground to risedramatically, scientists report.
The simmering volcano has produced major eruptions—each a thousandtimes more powerful than
Mount St. Helens's1980 eruption—three times in the past 2.1 million years. Yellowstone's caldera,which covers a 25- by 37-mile (40- by 60-kilometer) swath of Wyoming, is an ancient crater formed after the last bigblast, some 640,000 years ago.
(See "When YellowstoneExplodes" in National Geographic magazine.)
Since then, about 30 smaller eruptions—including one as recent as70,000 years ago—have filled the caldera with lava and ash, producing the relativelyflat landscape we see today.
But beginning in 2004, scientists saw the ground above the caldera riseupward at rates as high as 2.8 inches (7 centimeters) a year. (Related: "YellowstoneIs Rising on Swollen 'Supervolcano.'")
The rate slowed between 2007 and 2010 to a centimeter a year or less.Still, since the start of the swelling, ground levels over the volcano havebeen raised by as much as 10 inches (25 centimeters) in places.
"It's an extraordinary uplift, because it covers such a large areaand the rates are so high," said the
Universityof Utah's Bob Smith, a longtime expert in Yellowstone'svolcanism.
Scientists think a swelling magma reservoir four to six miles (seven toten kilometers) below the surface is driving the uplift. Fortunately, the surgedoesn't seem to herald an imminent catastrophe, Smith said. (Related: "UnderYellowstone, Magma Pocket 20 Percent Larger Than Thought.")
"At the beginning we were concerned it could be leading up to aneruption," said Smith, who co-authored a paper on the surge published inthe December 3, 2010, edition of Geophysical Research Letters.
"But once we saw [the magma] was at a depth of ten kilometers, weweren't so concerned. If it had been at depths of two or three kilometers [oneor two miles], we'd have been a lot more concerned."
Studies of the surge, he added, may offer valuable clues about what'sgoing on in the volcano's subterranean plumbing, which may eventually helpscientists predict when
Yellowstone's nextvolcanic "burp" will break out.
Smith and colleagues at the U.S.Geological Survey (USGS) Yellowstone Volcano Observatory have beenmapping the caldera's rise and fall using tools such as global positioningsystems (GPS) and interferometric synthetic aperture radar (InSAR), which givesground-deformation measurements.
Ground deformation can suggest that magma is moving toward the surfacebefore an eruption: The flanks of
Mount St. Helens,for example, swelled dramatically in the months before its 1980 explosion.(See pictures ofMount St. Helens before and after the blast.)
But there are also many examples, including the
Yellowstonesupervolcano, where it appears the ground has risen and fallen for thousands ofyears without an eruption.
According to current theory,
Yellowstone'smagma reservoir is fed by a plume of hot rock surging upward from Earth'smantle. (Related: "NewMagma Layer Found Deep in Earth's Mantle?")
When the amount of magma flowing into the chamber increases, thereservoir swells like a lung and the surface above expands upward. Modelssuggest that during the recent uplift, the reservoir was filling with 0.02cubic miles (0.1 cubic kilometer) of magma a year.
When the rate of increase slows, the theory goes, the magma likelymoves off horizontally to solidify and cool, allowing the surface to settleback down.
Based on geologic evidence, Yellowstone has probably seen a continuouscycle of inflation and deflation over the past 15,000 years, and the cycle willlikely continue, Smith said.
Surveys show, for example, that the caldera rose some 7 inches (18centimeters) between 1976 and 1984 before dropping back about 5.5 inches (14centimeters) over the next decade.
"These calderas tend to go up and down, up and down," hesaid. "But every once in a while they burp, creating hydrothermalexplosions, earthquakes, or—ultimately—they can produce volcaniceruptions."
Predicting when an eruption might occur is extremely difficult, in partbecause the fine details of what's going on under
Yellowstoneare still undetermined. What's more, continuous records of Yellowstone'sactivity have been made only since the 1970s—a tiny slice of geologictime—making it hard to draw conclusions.
"Clearly some deep source of magma feeds Yellowstone, and sinceYellowstone has erupted in the recent geological past, we know that there ismagma at shallower depths too," said Dan Dzurisin, a Yellowstone expertwith the USGS Cascades Volcano Observatory in
. Washington State
"There has to be magma in the crust, or we wouldn't have all thehydrothermal activity that we have," Dzurisin added. "There is somuch heat coming out of Yellowstone right now that if it wasn't being reheatedby magma, the whole system would have gone stone cold since the time of thelast eruption 70,000 years ago."
The large hydrothermal system just below Yellowstone's surface, whichproduces many of the park's top tourist attractions, may also play a role inground swelling, Dzurisin said, though no one is sure to what extent.
"Could it be that some uplift is caused not by new magma coming inbut by the hydrothermal system sealing itself up and pressurizing?" heasked. "And then it subsides when it springs a leak and depressurizes?These details are difficult."
And it's not a matter of simply watching the ground rise and fall.Different areas may move in different directions and be interconnected inunknown ways, reflecting the as yet unmapped network of volcanic andhydrothermal plumbing.
The roughly 3,000 earthquakes in
Yellowstoneeach year may offer even more clues about the relationship between grounduplift and the magma chamber.
For example, between December 26, 2008, and January 8, 2009, some 900 earthquakesoccurred in the area around
. Yellowstone Lake
This earthquake "swarm" may have helped to release pressureon the magma reservoir by allowing fluids to escape, and this may have slowedthe rate of uplift, the
's Smith said. (Related: "Mysterious'Swarm' of Quakes Strikes Oregon Waters.") University of Utah
"Big quakes [can have] a relationship to uplift and deformationscaused by the intrusion of magma," he said. "How those intrusionsstress the adjacent faults, or how the faults might transmit stress to themagma system, is a really important new area of study."
Overall, USGS's Dzurisin added, "the story of
Yellowstonedeformation has gotten more complex as we've had better and better technologiesto study it."