Link Between Yellowstone And The Magma Plume Found, Imaged

It is like finding a leak in your roof. I remember once up at the cabin, noticing that my waders were full of water and pointing this out to my wife.

"You're supposed to hang the waders upside down. Keeps dead mice from falling in there."

Well, I thought, if any mice fell in these waders and weren't dead, they'd drown for sure. Anyway, I traced the leak to a part of the ceiling in the closet. Eventually I was able to find the place in the attic where the water was probably going down into the closet, but by this time the torrential rain storms that had preceded the discovery of Lake Waders had long passed and I was going on indirect evidence. Over the next few weeks there were more storms, and every now and then I got to look at where the leak was tracing from but always lost track of it.

Finally, my father-in-law and I figured out how to do it. I got up on the roof with a hose, and he got in the attic with a flashlight. I kept pouring water and he kept tracing back drips until we finally found the perfectly round hole, hidden from view at the top by some recently grown lichen. It was an exit wound, like a .22 caliber bullet had exited the roof in an accidental discharge. Or maybe it was an entrance wound. Eventually I decided it must have been a meteor. No particular evidence for that, but it would be the coolest explanation.

Anyway that's how it has been over the last few decades at Yellowstone.

You know Yellowstone is one of the world's largest calderas. When it was formed, in a major explosive eruption about 650,000 years ago or so, it must have been a hell of a mess. If something like that happened there again it would totally ruin the day for anybody visiting the park. And, by "visiting the park" I mean living anywhere in North America pretty much.

Early on, Geologists knew there was a magma plume. This is equivalent, in my analogy, to the big rainstorm that provided the water for the leak in the roof. We know it is there because you can see it. As the North American continental plate moves along to the southwest, it passes over the plume, and the plume is the source for lots of volcanic activity including the occasional day-ruining super volcanic caldera eruption, the big Yellowstone eruption being the most recent of those. You can see all the older volcanic activity, and date it, in a somewhat curved line passing upwards in time along the surface of the continental plate. No problem identifying that.

But, how does the surface of Yellowstone, which puts enormous amounts of volcanic CO2 into the atmosphere continuously, has the largest hydro-thermal system on the planet, the occassional lava flow, etc. connect to the lava plume?

A while back scientists used seismic imaging to depict a fairly large and complex magma feature under the surface. This provides the immediate heat and gasses, but it was not large enough or deep enough to be the ultimate source or the connection to the deeper mantle of the earth. They were still in the attic trying to trace back the leak.

Now, scientists Hsin-Hua Huang, Fan-Chi Lin, Brandon Schmandt, Jamie Farrell, Robert B. Smith, Victor C. Tsai, in a paper titled "The Yellowstone magmatic system from the mantle plume to the upper crust," published in Science, have used even more seismic imaging to locate and map out a deeper, larger batch of magma that is the link between the molten hot deepens of the earth, the part under the continental plates, and the Yellowstone area.

From the Abstract:

The Yellowstone supervolcano is one of the largest active continental silicic volcanic fields in the world. An understanding of its properties is key to enhancing our knowledge of volcanic mechanisms and corresponding risk. Using a joint local and teleseismic earthquake P-wave seismic inversion, we unveil a basaltic lower-crustal magma body that provides a magmatic link between the Yellowstone mantle plume and the previously imaged upper-crustal magma reservoir. This lower-crustal magma body has a volume of 46,000 km3, ~4.5 times larger than the upper-crustal magma reservoir, and contains a melt fraction of ~2%. These estimates are critical to understanding the evolution of bimodal basaltic-rhyolitic volcanism, explaining the magnitude of CO2 discharge, and constraining dynamic models of the magmatic system for volcanic hazard assessment.

I love the use of the word "unveil" here. "Hey, Duane, I think I unveiled a bullet hole up here on the roof! There's your problem!"

Anyway, the details are strikingly complex and involved intense geological science. The implications are still a bit unclear. In a write-up by Eric Hand in Science, geophysicist Alan Lavender says this is “a comprehensive view of the magma system from the top of the plume into the crust. [But] this doesn’t exactly match up with our expectations.” Scientists had been expecting the offset between the upper and lower chambers to be in the opposite direction, west rather than east of the plume.

I don't know. Maybe they were just holding the map upside down. They need to stick a pencil through the hole to verify it as the true source, like Duane did while I was up there on the roof.

Caption for the image at the top of the post:

Fig. 4 Schematic model for the Yellowstone crust-to-upper mantle magmatic system.
The orientation of the model is along the cross-section AA′ in Fig. 3. The geometry of the upper and lower crustal magma reservoirs are based on the contour of 5% VP reduction in the tomographic model. The dashed outline of the lower crustal magma reservoir indicates the larger uncertainties in its boundaries relative to that of the upper reservoir (25). The white arrow indicates the North American plate

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I think they should start making plans to stabilize it in case it ever does start to be in danger of erupting.

By daedalus2u (not verified) on 24 Apr 2015 #permalink

Answering that is step 1.

Answering that for the result of step 1 is step 2.

By Chakat Firepaw (not verified) on 24 Apr 2015 #permalink

Step 3: ??????
Step 4: Profit!

By Michael Kelsey (not verified) on 24 Apr 2015 #permalink

Those percentages of melt seem awfully low to me. But, I don't know how high they must be before the rock can act like a highly viscous fluid.

I would think the Lake Toba eruption roughly 85,000 years ago was at least as big as Yellowstone. Genetic evidence points to the human breeding population having been reduced to a few thousand at some time near then.

I used to think the way to stop eruptions would be longterm deep geothermal heat extraction, (probably taking a few hundred years to have an effect). But, since then, I've read that cooling of a magma body can cause the lower melting point constituents to freeze and separate gravitationally, leading to an eruption of the now changed composition magma. It may be that even with a thousand year warning, and huge resources that we still wouldn't stop one.

By Omega Centauri (not verified) on 25 Apr 2015 #permalink

How I would resolve it would depend on what volatile is present. If it is water (the usual volatile), then removing the hydrogen by injecting carbon and forming methane is the way to do it.

2C + 2 H2O --> CH4 + CO2

If the volatile is CO2, that becomes more difficult, but the solution is still to inject carbon. Then the carbon is removed as CO

C + CO2 --> 2 CO

The solubility of gases in magma goes as H2O, CO2, CH4, CO.

What is needed is to inject carbon, remove the gases, process them to recover the carbon and reinject the carbon while generating enough power to run the system.

I agree with Omega Centauri, that simple cooling would not be effective, you need to change the composition and remove volatiles, or add non-volatiles.

Adding silicon, is another way to modify the composition. Ferrosilicon is another way. It is denser than magma, would sink to where it would melt and the silicon and eventually the iron would react with the gases.

By daedalus2u (not verified) on 26 Apr 2015 #permalink

Given the very slow rates of convection in these bodies, settling is probably not an issue. But cooling does lead to phase separation..

If (and I really don't quite know how you'd do this) you could put long reach wells into these bodies and extract all the volatile content - probably as some sort of water-CO2 critical fluid - you might both cool and 'defuse' the rhyolite body. Indeed, these hydrothermal fluids are what give rise to many economic mineral bodies, so not only would you get a LOT of energy out of these boreholes, you might also get a lot of quite valuable minerals.

Issue is that you have to somehow put a borehole into temperatures of hundreds of degrees, stabilize it, and extract fluids without the whole works gumming up. And a blowout could be *ahem* interesting.

By Andrew Dodds (not verified) on 27 Apr 2015 #permalink