Yellowstone's plumbing exposed

Dec 14, 2009
A cross section of the plume of hot and molten rock that tops out about 50 miles beneath Yellowstone National Park and tilts downward to the northwest to a depth of at least 410 miles. The plume is mostly hot rock with about 1 to 2 percent molten rock. Researches believe "blobs" of hot rock slowly detach from the top of the plume and rise upward to recharge the magma chamber that lies from 3.7 to 10 miles beneath Yellowstone. The chamber is also mostly hot rock, but with a sponge-like structure containing about 8 to 15 percent molten rock. Credit: University of Utah

(PhysOrg.com) -- The most detailed seismic images yet published of the plumbing that feeds the Yellowstone supervolcano shows a plume of hot and molten rock rising at an angle from the northwest at a depth of at least 410 miles, contradicting claims that there is no deep plume, only shallow hot rock moving like slowly boiling soup.

A related University of Utah study used gravity measurements to indicate the banana-shaped chamber of hot and a few miles beneath is 20 percent larger than previously believed, so a future cataclysmic eruption could be even larger than thought.

The study's of Yellowstone's plume also suggests the same "hotspot" that feeds Yellowstone volcanism also triggered the Columbia River "flood basalts" that buried parts of Oregon, Washington state and Idaho with lava starting 17 million years ago.

Those are key findings in four National Science Foundation-funded studies in the latest issue of the Journal of Volcanology and Geothermal Research. The studies were led by Robert B. Smith, research professor and professor emeritus of geophysics at the University of Utah and coordinating scientist for the Yellowstone Volcano Observatory.

"We have a clear image, using seismic waves from earthquakes, showing a mantle plume that extends from beneath Yellowstone,'' Smith says.

The plume angles downward 150 miles to the west-northwest of Yellowstone and reaches a depth of at least 410 miles, Smith says. The study estimates the plume is mostly hot rock, with 1 percent to 2 percent molten rock in sponge-like voids within the hot rock.

Some researchers have doubted the existence of a mantle plume feeding Yellowstone, arguing instead that the area's volcanic and hydrothermal features are fed by convection - the boiling-like rising of hot rock and sinking of cooler rock - from relatively shallow depths of only 185 miles to 250 miles.

The Hotspot: A Deep Plume, Blobs and Shallow Magma

Some 17 million years ago, the Yellowstone hotspot was located beneath the Oregon-Idaho-Nevada border region, feeding a plume of hot and molten rock that produced "caldera" eruptions - the biggest kind of volcanic eruption on Earth.

As North America slid southwest over the hotspot, the plume generated more than 140 huge eruptions that produced a chain of giant craters - calderas - extending from the Oregon-Idaho-Nevada border northeast to the current site of Yellowstone National Park, where huge caldera eruptions happened 2.05 million, 1.3 million and 642,000 years ago.

These eruptions were 2,500, 280 and 1,000 times bigger, respectively, than the 1980 eruption of Mount St. Helens. The eruptions covered as much as half the continental United States with inches to feet of volcanic ash. The Yellowstone caldera, 40 miles by 25 miles, is the remnant of that last giant eruption.

The new study reinforces the view that the hot and partly molten rock feeding volcanic and geothermal activity at Yellowstone isn't vertical, but has three components:

  • The 45-mile-wide plume that rises through Earth's upper mantle from at least 410 miles beneath the surface. The plume angles upward to the east-southeast until it reaches the colder rock of the North American crustal plate, and flattens out like a 300-mile-wide pancake about 50 miles beneath Yellowstone. The plume includes several wider "blobs" at depths of 355 miles, 310 miles and 265 miles.

    "This conduit is not one tube of constant thickness," says Smith. "It varies in width at various depths, and we call those things blobs."

  • A little-understood zone, between 50 miles and 10 miles deep, in which blobs of hot and partly molten rock break off of the flattened top of the plume and slowly rise to feed the magma reservoir directly beneath Yellowstone National Park.
  • A magma reservoir 3.7 miles to 10 miles beneath the Yellowstone caldera. The reservoir is mostly sponge-like hot rock with spaces filled with molten rock.

    "It looks like it's up to 8 percent or 15 percent melt," says Smith. "That's a lot."

Researchers previously believed the magma chamber measured roughly 6 to 15 miles from southeast to northwest, and 20 or 25 miles from southwest to northeast, but new measurements indicate the reservoir extends at least another 13 miles outside the caldera's northeast boundary, Smith says.

He says the gravity and other data show the magma body "is an elongated structure that looks like a banana with the ends up. It is a lot larger than we thought - I would say about 20 percent [by volume]. This would argue there might be a larger magma source available for a future eruption."

Images of the magma reservoir were made based on the strength of Earth's gravity at various points in Yellowstone. Hot and molten rock is less dense than cold rock, so the tug of gravity is measurably lower above magma reservoirs.

The Yellowstone caldera, like other calderas on Earth, huffs upward and puffs downward repeatedly over the ages, usually without erupting. Since 2004, the caldera floor has risen 3 inches per year, suggesting recharge of the magma body beneath it.

Seismic imaging was used by University of Utah scientists to construct this 3-D picture of the Yellowstone hotspot plume of hot and molten rock that feeds the shallower magma chamber (not shown) beneath Yellowstone National Park, outlined in green at the surface, or top of the illustration. The Yellowstone caldera, or giant volcanic crater, is outlined in red. State boundaries are shown in black. The park, caldera and state boundaries also are projected to the bottom of the picture to better illustrate the plume's tilt. Researchers believe "blobs" of hot rock float off the top of the plume, then rise to recharge the magma chamber located 3.7 miles to 10 miles beneath the surface at Yellowstone. The illustration also shows a region of warm rock extending southwest from near the top of the plume. It represents the eastern Snake River Plain, where the Yellowstone hotspot triggered numerous cataclysmic caldera eruptions before the plume started feeding Yellowstone 2.05 million years ago. Credit: University of Utah

How to View a Plume

Seismic imaging uses earthquake waves that travel through the Earth and are recorded by seismometers. Waves travel more slowly through hotter rock and more quickly in cooler rock. Just as X-rays are combined to make CT-scan images of features in the human body, data are melded to produce images of Earth's interior.

The study, the Yellowstone Geodynamics Project, was conducted during 1999-2005. It used an average of 160 temporary and permanent seismic stations - and as many as 200 - to detect waves from some 800 earthquakes, with the stations spaced 10 miles to 22 miles apart - closer than other networks and better able to "see" underground. Some 160 Global Positioning System stations measured crustal movements.

By integrating seismic and GPS data, "it's like a lens that made the upper 125 miles much clearer and allowed us to see deeper, down to 410 miles," Smith says.

The study also shows warm rock - not as hot as the plume - stretching from Yellowstone southwest under the Snake River Plain, at depths of 20 miles to 60 miles. The rock is still warm from eruptions before the hotspot reached Yellowstone.

A Plume Blowing in the 2-inch-per-year Mantle Wind

Seismic imaging shows a "slow" zone from the top of the plume, which is 50 miles deep, straight down to about 155 miles, but then as you travel down the plume, it tilts to the northwest as it dives to a depth of 410 miles, says Smith.

That is the base of the global transition zone - from 250 miles to 410 miles deep - that is the boundary between the upper and lower mantle - the layers below Earth's crust.

At that depth, the plume is about 410 miles beneath the town of Wisdom, Mont., which is 150 miles west-northwest of Yellowstone, says Smith.

He says "it wouldn't surprise me" if the plume extends even deeper, perhaps originating from the core-mantle boundary some 1,800 miles deep.

Why doesn't the plume rise straight upward? "This plume material wants to come up vertically, it wants to buoyantly rise," says Smith. "But it gets caught in the 'wind' of the upper mantle flow, like smoke rising in a breeze." Except in this case, the "breeze" of slowly flowing upper mantle rock is moving horizontally 2 inches per year.

While the crustal plate moves southwest, the warm, underlying mantle slowly boils due to convection, with warm areas moving upward and cooler areas downward. Northwest of Yellowstone, this convection is such that the plume is "blown" east-southeast by mantle convection, so it angles upward toward Yellowstone.

Scientists have debated for years whether Yellowstone's volcanism is fed by a plume rising from deep in the Earth or by shallow churning in the upper mantle caused by movements of the overlying crust. Smith says the new study has produced the most detailed image of the Yellowstone plume yet published.

But a preliminary study by other researchers suggests Yellowstone's plume goes deeper than 410 miles, ballooning below that depth into a wider zone of hot rock that extends at least 620 miles deep.

The notion that a deep plume feeds Yellowstone got more support from a study published this month indicating that the Hawaiian hotspot - which created the Hawaiian Islands - is fed by a plume that extends downward at least 930 miles, tilting southeast.

A Common Source for Yellowstone and the Columbia River Basalts?

Based on how the Yellowstone plume slants now, Smith and colleagues projected on a map where the plume might have originated at depth when the hotspot was erupting at the Oregon-Idaho-Nevada border area from 17 million to almost 12 million years ago.

They saw overlap, between the zones within the Earth where eruptions originated near the Oregon-Idaho-Nevada border and where the famed Columbia River Basalt eruptions originated when they were most vigorous 17 million to 14 million years ago.

Their conclusion: the Yellowstone hotspot might have fed those gigantic lava eruptions, which covered much of eastern Oregon and eastern Washington state.

I argue it is the common source," Smith says. "It's neat stuff and it fits together."

Smith conducted the seismic study with six University of Utah present or former geophysicists - former postdoctoral researchers Michael Jordan, of SINTEF Petroleum Research in Norway, and Stephan Husen, of the Swiss Federal Institute of Technology; postdoc Christine Puskas; Ph.D. student Jamie Farrell; and former Ph.D. students Gregory Waite, now at Michigan Technological University, and Wu-Lung Chang, of National Central University in Taiwan. Other co-authors were Bernhard Steinberger of the Geological Survey of Norway and Richard O'Connell of Harvard University.

Smith conducted the gravity study with former University of Utah graduate student Katrina DeNosaquo and Tony Lowry of Utah State University in Logan.

Source: University of Utah (news : web)

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SincerelyTwo
4.5 / 5 (2) Dec 14, 2009
This is mind blowing, it's amazing how large and beastly that plume is, and for the longest time our only understanding of it was that tiny tip at the surface ... and that tiny tip was huge to us!

It's not often I'm drawn in to geology, but this is absurd. I recently watched a documentary which described one of the reasons for some larger extinctions on record was due to this furious beast exploding.

Makes me wonder, should we prematurely cause super volcanoes like this to release energy from building pressure on some regular interval? ... to protect our long term interests from cataclysmic destruction.

Maybe we should drill deep holes in to these systems somehow, or would that make the situation worse?

Better yet, we should convert yellowstone in to a geothermal power system, I know we'd destroy some beautiful landscapes, but beautiful things can become quite furious... and especially dangerous.
frajo
1.7 / 5 (3) Dec 14, 2009
Yellowstone National Park, where huge caldera eruptions happened 2.05 million, 1.3 million and 642,000 years ago.
Nobody knows whether this pattern will continue. But if it does then it will be beyond the wit of mankind.
Birger
4 / 5 (1) Dec 14, 2009
The composition of the magma is different from more "calm" volcanic systems, such as the Hawaian hot spot, this is why the system erupts cataclysmically. I suppose it would not be feasible to inject enough matter to alter the properties of the magma, but cooling would slow down the upwelling.
Iceland is doing research on really deep geothermal power drilling, but the credit crunch has probably slowed down the work.
stonehat
1 / 5 (1) Dec 14, 2009
Yes, yes, very interesting, but do you think it might also have been interesting for your readers to have maybe at least asked the authors of this work "Will it erupt soon and will that eruption spell the end of the human race?" ?!

Nik_2213
1 / 5 (1) Dec 14, 2009
Now, will it continue to smear sideways, or break away and create a new surface feature ??
frajo
1.5 / 5 (2) Dec 14, 2009
will that eruption spell the end of the human race?
Improbable as homo sapiens survived even the Toba event 75 Kyears ago. Homo Americanus Borealis might be less lucky.
defunctdiety
5 / 5 (1) Dec 14, 2009
Now, will it continue to smear sideways, or break away and create a new surface feature ??

The answer is, both.

Like Hawaii the hot spot doesn't move, the surface does, it will continue to "smear sideways" as you put it. As it does the old geological surface spot will move father out from over the hotspot and eventually break away and cease to be active (once it's too far from the hot spot to be fueled by it anymore), it will fade away with time (much like the tailing Hawaiian islands) probably leaving some pretty cool underground caves.

When the plume is "cut off" by the shear, as is guaranteed eventually, it will push up anew until it has another catastrophic eruption I imagine, then forming your new surface feature.

In other words, if that thin spot in the image of the plume starts to develop a new hump upstream, more directly over the origin of the plume, that's probably when we'll have to start worrying about a new eruption, ya know in a few hundred thousand years or so.
defunctdiety
4.3 / 5 (3) Dec 14, 2009
Well, disregard the above, at least partially...I just realized the continental plate is moving the opposite direction of the plume (i.e. plume is angled NE, plate is/was drifting SW)...

You can see the historic "path" of the hot spot on a topographical map I think...it basically swept in a smile-like shape (a flattened u) through southern Idaho (perhaps roughly I-84 into I-86 then north-east), if the crust keeps going on that trajectory, Yellowstone will gradually move into southern Montanta I suppose, creating new surface features as it goes, the old ones fading away.

That's my 2-cents, formed from nothing more than my own limited knowledge :P
Dutchtraveller
4.3 / 5 (3) Dec 14, 2009
I have also been thinking about using the yellowstone magma chamber as a powersource. Cooling the magma down should lower the chance of eruptions unless we weaken the crust too much.
So I did a back of the envelope calculation.
According to the USGS the volume of the magma chamber is 15.000 cubic kilometers.
Assuming a density of 2500kg/m3 and specific heat of 1kJ/kg/K.
To lower the temperature by 1 degree we would have to extract almost 4x10^19J.
That's approx. 1250GW of thermal power for 1 year.
At 35-40% efficiency that would yield 400-500GW electric.
But since the magma chamber is still fed from the plume we should be able to extract energy at this level for hundreds of years.
Just need to avoid triggering an eruption.
Takes a bit of water though...
Sean_W
3.7 / 5 (3) Dec 14, 2009
The concept of releasing pressure of a volcanic upwell sounds helpful, it might not be. I am no geologist but I seem to recall that the properties of magma is partially dependant on its pressure. At the mantle, material is almost solid dispite high temperature. As a part of the crust thins, like where plates are separating, the decompression causes some of the mantle to liquify and produce volcanos. While magma extrusions are already fairly liquid clompared to surounding material, lowering the pressure could make it less viscous and able to force itself to the surface and disolved gasses could bubble out like a shaken pop bottle when opened.

I'm not saying it deffinately should not be tried, but I would want to learn a lot more and maybe try it on a smaller, more issolated system first.
StillWind
2.8 / 5 (4) Dec 14, 2009
The idea that we could avert an eruption is as absurd as the idea that we can change the weather. These forces are so beyond the scope of humanity, that nothing we could do would have even the slightest effect on them.
Although geothermal energy should be a no-brainer.
SincerelyTwo
3 / 5 (2) Dec 14, 2009
StillWind, comparing the two is absurd. We're talking about an underground pressure building over millions of years, and that's pressure being applied over a broad area. If all of that energy were exerted in a single spot, which it isn't, it would already have broken through. We can't control the explosion, we can't control the inevitability of it, we can't stop the earth from doing it's thing, but we can drill a damn hole and use explosives to prematurely provoke the volcano at a point where it would have a far less severe impact on our society.

Why is it so hard for people to think. It's like you convinced yourself it's impossible, based on no actual reasoning or thought other than 'just because, it's big man... so big, so out of control maaannn'.

We can in fact change the distribution of gases in our atmosphere. We ARE COMPLETELY capable of AFFECTING SOME change. We should apply the most effective action we can, in a critical way.
Nartoon
4.7 / 5 (3) Dec 15, 2009
Yellowstone National Park, where huge caldera eruptions happened 2.05 million, 1.3 million and 642,000 years ago.
--------------------------------
By my calculations the time between the first and second eruptions was 750,000 years, between the second and third was 658,000 years. Since it's been 642,000 years since the last explosion I'd say we're in the ballpark for fireworks in the near future geologically speaking.
frajo
2.7 / 5 (3) Dec 15, 2009
We can in fact change the distribution of gases in our atmosphere.
But not in the lithosphere.
We ARE COMPLETELY capable of AFFECTING SOME change.
We can't divert a slab of molten rock with 500 km depth. And if we drill holes into the magma chamber 5 km underneath we only accelerate the outflow of 1000 degree Celsius lava streams to cover huge areas.
We should apply the most effective action we can, in a critical way.
Nuclear bombs? To which avail?
SincerelyTwo
2 / 5 (2) Dec 15, 2009
frajo; We can let it blast with all its might and cover 1/2 of our nation in destruction, or maybe we can get away with only 1/3-1/4 of our nation being destroyed. The affects are going to be massive, the 10-20% we can salvage will be worth it. Then again, judging by how close we are to the next explosion it might already be too late anyway.

It seems insane to care now because nothing is happening, but maybe we should already be moving our farm lands in preparation for the next few thousand years. We have the tools and data to know in advance about how close we are to the catastrophe, we'd be idiots to ignore it and do nothing at all.

Because we as individuals exist for 3/4 of a century at a time shouldn't justify being irresponsible for the future of our species.

Screw it, you guys can be r-tards, I'll just move to some other continent and breed there, hoping to sow my future clones in a more secure place.

This should be obvious.
RJ32
3.5 / 5 (2) Dec 15, 2009
It seems to me that every time man attempts to avert a disaster, he creates a larger one.
Caliban
1 / 5 (1) Dec 15, 2009
The problem with tapping off the available heat is this- if you inject water into or near the plume, the heat uptake can cool the rock in the area enough to cause fracturing. this in turn, reduces the pressure(on the order of many thousands of atmospheres)on the adjacent material, which could lead to further liquefaction, and FORCEFUL injection into the fractured surrounding rock, with highly unpredictable results, which could, conceiveably lead to an eruption. Same problem with trying to drill "relief" wells, or whatever- this material is under immensely more pressure than say, an oil field.
Going
not rated yet Dec 20, 2009
The heat in this magma has come from radioactive decay of elements deep in the Earth. The heat is trapped by the bulk of the earth and thermodynamically must seek a state of equilibrium through conduction of convection to cooler areas. Here we see a convection process. It would not be beyond the wit of future generations to see this flow of heat as a natural resource and harvest it near the surface. Perhaps a grid of geothermal stations over the whole area extracting heat in a slow controlled way so as not to open any sudden release of pressure.