The Oil Drum | DrumBeat: January 5, 2009

199 comments on DrumBeat: January 5, 2009

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Ignorant on January 5, 2009 - 10:39am

Concerning the Yellowstone Supervolcano:

I created and played around with a theoretical model this weekend. My opinion is that there's a low propability that it will go off in one huge explosion.

More likely: it will start as an average volcano... except that it'll keep on going... and going... for years... then decades... maybe even centuries. When enough ash is vented my model breaks down since I don't know how the dome's collapse would happen (might seal the vent... or open new ones). I don't have the geological data to model a collapse.

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Darwinian on January 5, 2009 - 11:40am

My opinion is that there's a low propability that it will go off in one huge explosion.

More likely: it will start as an average volcano... except that it'll keep on going... and going... for years... then decades... maybe even centuries.

Impossible! That is, it is impossible for a supervolcano to erupt as an average volcano. That is because of the size of the magma chamber. The pressure per cubic meter is no greater than that of the average volcano, perhaps evens less, but because the magma chamber is several hundred times as massive, once the cap is breached all that pressure would be released at once.

The last supervolcano, Toba, erupted about 74,000 years ago and almost wiped out humankind. There is no evidence of any supervolcano erupting as a regular volcano and lasting for decades. Again, it is because of the enormous size of their magma chamber. When a supervolcano goes, it goes suddenly.

Anyway, Yellowstone has erupted at least three times in the past, probably more. Every time it erupted as a supervolcano and left only a caldera. Why on earth would you expect it to be different the next time?

Ron Patterson

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darwinsdog on January 5, 2009 - 12:06pm

Re: Toba eruption: Depends on how you define "humankind." My contention is that by virtue of wiping out competing central Eurasian populations of Homo erectus & H. neandertalensis, Toba facilitated the diaspora of African H. sapiens. So if you include our congeners in "humankind" your statement that Toba "almost wiped out humankind" may have some validity. But if you only count our own species as "human," Toba did us a big favor.

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Ignorant on January 5, 2009 - 12:29pm

If you get enough ash thrown out over a long-enough period it'll screw up anyone's day... probably worse than a one-time explosion.

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ericy on January 5, 2009 - 12:06pm

I would imagine that any super-eruptions will have destroyed much of the evidence for normal eruptions if there had been any.

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Darwinian on January 5, 2009 - 12:29pm

I would imagine that any super-eruptions will have destroyed much of the evidence for normal eruptions if there had been any.

Not so! It would have destroyed the cone of course but not massive lava flows that extended beyond the caldera. There are none around Yellowstone. We could expect, from a magma chamber that is about a thousand times that of a normal volcano, enermous amounts of lava flows if it erupted as a normal volcano. That simply did not happen.

Ron Patterson

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Ignorant on January 5, 2009 - 12:35pm

Some volcanoes produce magma flows... other produce ash. It depends on the magma.

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rainsong on January 6, 2009 - 8:02am

The eruption of Thera blew the volcano into oblivian and covered the island in ash. Krakatoa was a phreatic explosion instead of the less viscous flows characterized at Kilauea

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Ignorant on January 5, 2009 - 12:33pm

A dome collapse would pretty much destroy the structure of the volcanic cone. I think that the physical collapse of Thera and Krakatoa probably did as much - or more - to bring on the tsunami as any internal explosion did.

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rainsong on January 5, 2009 - 1:03pm

Yellowstone erupted spreading ash over hundreds of miles. If it were to erupt again it might precipitate an ice age.

http://www.solcomhouse.com/yellowstone.htm

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Ignorant on January 5, 2009 - 1:31pm

Concerning SOLCOMHOUSE link:

I stand educated about the post-collapse sequence, but I still think the PROBABILITY of a "rapid" magma depletion is OVER-exaggerated. Personally, I think it MORE PROBABLE that a "slow" lomg-term magma depletion is what initiates the collapse; something like a decade's/century's long Mt. St.-Helens-type event.

Not mentioned in link: largest volcanic dome in US is under the Adirondack Mountains in New York State. It just never erupted, so nobody's paid any attention to it... except some geologists. It's a fairly young feature; some estimates put it close to 5 million years old.

Adirondacks... "Young mountains, old rocks"

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Ignorant on January 5, 2009 - 12:26pm

Darwinian,

AAAaaa, but if the volcanic tube is long enough - and RELATIVELY narrow enough - (think Reynold's number) then the pressure gradient over the magma chamber will be slight enough that you wouldn't get the sudden pressure drop that everyone seems to assume.

Now, if an asteroid hit the dome, that would be another story.

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Paleocon on January 5, 2009 - 12:28pm

Haven't all the eruptions since 600K years ago been "normal" eruptions? The rhyolite fields that cover Yellowstone today were from the latter eruptions, 70K years ago, were they not?

From Wikipedia, both sorts can happen:

Non-explosive eruptions of lava and less violent explosive eruptions have occurred in and near the Yellowstone caldera since the last supereruption. The most recent lava flow occurred about 70,000 years ago while the largest violent eruption excavated the West Thumb of Lake Yellowstone around 150,000 years ago. Smaller steam explosions occur as well; an explosion 13,800 years ago left a 5 kilometer diameter crater at Mary Bay on the edge of Yellowstone Lake (located in the center of the caldera).[7][8] Currently, volcanic activity is exhibited only via numerous geothermal vents scattered throughout the region, including the famous Old Faithful Geyser.

The volcanic eruptions, as well as the continuing geothermal activity, are a result of a large chamber of magma located below the caldera's surface. The magma in this chamber contains gases that are kept dissolved only by the immense pressure that the magma is under. If the pressure is released to a sufficient degree by some geological shift, then some of the gases bubble out and cause the magma to expand. This can cause a runaway reaction. If the expansion results in further relief of pressure, for example, by blowing crust material off the top of the chamber, the result is a very large gas explosion.

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HankF on January 5, 2009 - 1:20pm

I thought that Yellowstone was caused by a crustal hot spot similar to the Hawaiian Islands. All you have to do is follow its path west to the lava flows in Idaho and Washington. Maybe the hot spot is on the move east again.

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