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article imageOp-Ed: Yellowstone magma measured at 36,000 atmospheres

By Paul Wallis     Jan 5, 2014 in Science
Grenoble - An independent ball of magma, pressurized to 36,000 atmospheres, has been identified under Yellowstone. The magma is said to be able to erupt “without any external trigger”.
That not-quite-cryptic-enough expression means the caldera can blow under its own steam, if you’ll excuse the expression, without interaction with other forces. It’s not dependent on feeds of magma from the mantle or earthquakes to detonate, for example.
The Independent:
Scientists have analysed magma from the Yellowstone caldera, a 55-mile-wide underground cavern containing between 200 and 600 cubic kilometres of molten rock, to see how it responds to changes in pressure and temperature.
“The difference in density between the molten magma in the caldera and the surrounding rock is big enough to drive the magma from the chamber to the surface,” said Jean-Philippe Perrillat of the National Centre for Scientific Research in Grenoble.
Yellowstone National Park actually sits on top of four over-lapping calderas.
Yellowstone National Park actually sits on top of four over-lapping calderas.
Kelvin Case
While a lot of gruesome fiction has been produced on the subject of super volcanoes, the known facts about "ordinary" volcanoes are terrifying enough:
1. In 535 AD, dendochronologists note an almost total absence of growth in tree rings in Ireland believed to be caused by volcanic eruptions in Indonesia. The sunlight was blocked, “like an eclipse”, according to ancient records. Fogs were reported in the Middle East, and crop failures caused famine.
2. Mount Hatepe in New Zealand erupted in 180 AD, sending pyroclastic flows 50km away from the epicentre.
3. In 1669, Mount Etna opened a 7 mile wide lava flow.
4. In 1815, Mount Tambora in Indonesia erupted, causing the “year without a summer in Europe”.
5. In 1883, Krakatoa produced a 37 mile high ash cloud, filled the Sunda Strait with pumice, and killed at least 30,000 people.
6. In 1902, Mount Pelee wiped out almost the entire population of St. Pierre and refugees from surrounding areas with pyroclastic flows, about 28,000 people.
These were the results of “conventional” eruptions. The difference is that Yellowstone is a super volcano. It has erupted before.
The US Geological Survey (USGS) has a page on Yellowstone. According to the USGS prior eruptions have been mainly lava flows. About 80 eruptions have been identified.
The USGS also doesn’t think an eruption is likely on its Yellowstone page:
QUESTION: Do scientists know if a catastrophic eruption is currently imminent at Yellowstone?
ANSWER: There is no evidence that a catastrophic eruption at Yellowstone is imminent, and such events are unlikely to occur in the next few centuries. Scientists have also found no indication of an imminent smaller eruption of lava.
QUESTION: How far in advance could scientists predict an eruption of the Yellowstone volcano?
ANSWER: The science of forecasting a volcanic eruption has significantly advanced over the past 25 years. Most scientists think that the buildup preceding a catastrophic eruption would be detectable for weeks and perhaps months to years. Precursors to volcanic eruptions include strong earthquake swarms and rapid ground deformation and typically take place days to weeks before an actual eruption. Scientists at the Yellowstone Volcano Observatory (YVO) closely monitor the Yellowstone region for such precursors. They expect that the buildup to larger eruptions would include intense precursory activity (far exceeding background levels) at multiple spots within the Yellowstone volcano. As at many caldera systems around the world, small earthquakes, ground uplift and subsidence, and gas releases at Yellowstone are commonplace events and do not reflect impending eruptions.
The USGS calculates the odds against an eruption as “730,000 to 1” on a yearly basis.
Scenarios- What a really big eruption might do
The probability of the entire magma field erupting is the worst case scenario. At a pressure of 36,000 atmospheres, the best analogy is a major nuclear strike. The result of a major detonation would be to displace an enormous volume of air, with massive shock waves. Depending on the physical values of the pressure of the waves and atmospheric pressures, both displaced and on impact, the direct effects of the blast could be felt across America. The atmosphere will also rush back in, like after a high explosive detonation, a double whammy.
Air pressures alone in both events could be catastrophic.
(At a pressure of 2 atmospheres, even balance and hearing can be affected. At multiple atmospheres, anything is possible. The range of effects depends on how much energy is transferred into the atmosphere during the detonation and the recoil of the atmosphere. An analogy would be deep water diving, “instant bends” caused by atmospheric pressures.
The Rockies would provide some shielding from the blast to the west, but the plains, north east and south would take an almost unrestricted blast. The inrush of returning winds after the explosion could be at hurricane force intensity, regardless of mountain ranges. Like Mt. St. Helens, but on an infinitely larger scale, the air pressure alone could flatten forests and anything else they hit.
Pyroclastic flows: These are caused when rock and materials vaporize. They’re a combination of these materials and gases, and are like 100 mph flame throwers racing along the ground surface, obliterating everything in their way. Pyroclastic flows caused the Pompeii disaster, as well as St. Pierre. Very large pyroclastic flows could annihilate areas around the eruption site.
Radiant heat would cover a large area around the caldera at lava temperatures, approximately 700-1200C. This would be a “local event” of several hundred square miles.
Tectonic effects: Unknown. An eruption would at least cause local earthquakes. In theory, the movement of large amounts of rock should affect tectonic dynamics to some degree, but it’s really guesswork.
The worst effects, ironically, would be after the explosion. Climate disruption would be inevitable, and the toxic materials deposited by a super volcano could spread around the world, as sulfates from major volcanoes are believed to have done in prior eruptions.
Large amounts of ash in the atmosphere could block sunlight, globally, as in prior examples. Crop failure and pollution through microparticulates could be extremely serious. Respiratory effects would be inevitable, a sort of “global asthma” possible at a certain range of parts per million in the atmosphere. Contamination of dams and reservoirs would be a likely scenario.
Blocking photosynthesis could also add serious problems in terms of the global environment. Super volcanoes are believed responsible for previous mass extinctions, and it’s not hard to see why. Crashing the various environmental cycles, like the water, carbon, nitrogen cycles, could disrupt a wide range of biological processes.
Microbiological processes are also likely to be severely disrupted in the blast area and highly reactive in areas affected by chemical processes from the volcanic materials.
The good news, such as it is, is that Yellowstone’s dynamics don’t seem prone to explosive events. The magma seems comparatively stable. Sporadic lava flows are much more likely. The new information has added another element to the puzzle, but not a basis for prediction.
The grey area is that while the current situation appears stable, what happens if more materials are added from the mantle, or a change to the chemical/gas mix appears in the caldera? Let’s hope we don’t find out. 36,000 atmospheres is a lot of pressure. At that pressure, a gas cylinder, let alone a super volcano, would create a massive explosion. If that blows, dig a hole and hope for the best.
This opinion article was written by an independent writer. The opinions and views expressed herein are those of the author and are not necessarily intended to reflect those of
More about Yellowstone super volcano, USGS, pyroclastic flows, JeanPhilippe Perrillat, National Centre for Scientific Research Grenoble
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