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LookingSkyward
2017-Feb-15, 07:38 PM
http://www.dailymail.co.uk/sciencetech/article-4226566/Scientists-discover-massive-reservoir-greenhouse-gases.html

I found this interesting...

Reality Check
2017-Feb-15, 08:37 PM
A rather hyped Daily Mail article!
The discovery itself is interesting. The paper is Pervasive upper mantle melting beneath the western US (http://www.sciencedirect.com/science/article/pii/S0012821X16307543/)

We report from converted seismic waves, a pervasive seismically anomalous layer above the transition zone beneath the western US. The layer, characterized by an average shear wave speed reduction of 1.6%, spans over an area of ∼1.8106 km2∼1.8106 km2 with thicknesses varying between 25 and 70 km. The location of the layer correlates with the present location of a segment of the Farallon plate. This spatial correlation and the sharp seismic signal atop of the layer indicate that the layer is caused by compositional heterogeneity. Analysis of the seismic signature reveals that the compositional heterogeneity can be ascribed to a small volume of partial melt (0.5 0.2 vol% on average). This article presents the first high resolution map of the melt present within the layer. Despite spatial variations in temperature, the calculated melt volume fraction correlates strongly with the amplitude of PS conversion throughout the region. Comparing the values of temperature calculated from the seismic signal with available petrological constraints, we infer that melting in the layer is caused by release of volatiles from the subducted Farallon slab. This partially molten zone beneath the western US can sequester at least 1.21017 kg1.21017 kg of volatiles, and can act as a large regional reservoir of volatile species such as H or C.

CJSF
2017-Feb-15, 09:06 PM
I wish the map was generally available.
[edit: Oh, I see a version in the article, now]

Also, the Daily Mail article slyly implies that "natural" CO2 inputs are more important that human ones, regarding global warming. The denier contacts I have are already spinning it.

CJSF

kzb
2017-Feb-16, 12:17 PM
Fracking on steroids :) 217 miles deep.

Really this is interesting, because although abiogenic oil has been largely discounted, here we have an alternative product, which could be fairly described as such. It's just a bit deeper than they said.

Swift
2017-Feb-16, 01:44 PM
I'm curious what the form of this material is. It seems to be described as "carbon", though the abstract quoted above actually says "can act as a large regional reservoir of volatile species such as H or C". My suspicion is that it is not molten, elemental carbon, but some sort of material closer to tar, some sort of hydrocarbon mixture with a very high molecular weight and a high carbon/hydrogen ratio.

CJSF
2017-Feb-16, 02:37 PM
Could it be carbonitite?

CJSF

Swift
2017-Feb-16, 03:50 PM
Could it be carbonitite?

CJSF
Yeah, I was thinking molten carbonates too. I was mostly thinking it probably isn't elemental carbon.

WaxRubiks
2017-Feb-16, 03:54 PM
Toffee?

Swift
2017-Feb-16, 05:56 PM
Toffee?
You wish. :D

kzb
2017-Feb-16, 05:57 PM
Quote from abstract:

This partially molten zone beneath the western US can sequester at least 1.21017 kg1.21017 kg of volatiles, and can act as a large regional reservoir of volatile species such as H or C.

"H" and "C" are identified.

The melting point of say calcium carbonate is very high and would not normally be classed as a "volatile".

It wouldn't be normal to think of carbonates as volatiles.

So I think it is most likely they mean hydrocarbons of some sort.

BigDon
2017-Feb-16, 06:28 PM
I was actually going to post that article to complain about bad science and sensationalism.

Noisy Rhysling
2017-Feb-16, 06:35 PM
So I think it is most likely they mean hydrocarbons of some sort.

Oh Cthulhu, don't even imply that. Some idiot will be wanting to drill...

BigDon
2017-Feb-16, 06:42 PM
Actually Chief that idiot in question probably wouldn't have a choice if this is the case.

Swift
2017-Feb-16, 09:47 PM
Quote from abstract:

This partially molten zone beneath the western US can sequester at least 1.21017 kg1.21017 kg of volatiles, and can act as a large regional reservoir of volatile species such as H or C.

"H" and "C" are identified.

The melting point of say calcium carbonate is very high and would not normally be classed as a "volatile".

It wouldn't be normal to think of carbonates as volatiles.

So I think it is most likely they mean hydrocarbons of some sort.
That was my initial thought. But we're not talking about single phase carbonates probably, we're talking about complex mixtures. From this reference (https://arxiv.org/ftp/arxiv/papers/1209/1209.3512.pdf):

Li2CO3 has a lower melting point (mp 723C), than Na2CO3 (mp 851C) or K2CO3 (mp 891C), but a mix of the salts has lower melting point. We have previously explored effective electrolyses in both the pure Li2CO3 melt, and a Li0.90Na0.62K0.48CO3 melt. Mixed alkali carbonate melting points can be low, including 399C for this eutectic Li0.90Na0.62K0.48CO3 mix, and 695C for the Na1.23K0.77CO3 eutectic salts. The addition of calcium carbonate can decrease the melting point of a carbonate mix.

Going by this wikipedia article (https://en.wikipedia.org/wiki/Geothermal_gradient), you'd estimate we'd be over 600C at 25 km. So I don't know that we can rule out carbonates.

bknight
2017-Feb-17, 02:25 AM
That was my initial thought. But we're not talking about single phase carbonates probably, we're talking about complex mixtures. From this reference (https://arxiv.org/ftp/arxiv/papers/1209/1209.3512.pdf):


Going by this wikipedia article (https://en.wikipedia.org/wiki/Geothermal_gradient), you'd estimate we'd be over 600C at 25 km. So I don't know that we can rule out carbonates.

But at those temperatures and pressures unlikely to be hydrocarbons.

kzb
2017-Feb-17, 10:43 AM
That was my initial thought. But we're not talking about single phase carbonates probably, we're talking about complex mixtures. From this reference (https://arxiv.org/ftp/arxiv/papers/1209/1209.3512.pdf):


Going by this wikipedia article (https://en.wikipedia.org/wiki/Geothermal_gradient), you'd estimate we'd be over 600C at 25 km. So I don't know that we can rule out carbonates.

There's no "H" in the formula though. Also, an eruption of carbonate salts wouldn't affect the climate in the way implied.

I can only access the abstract, not the full article. Maybe it is more clear in the full text.

As to whether the high temperature and pressure rule out hydrocarbons, not so sure either. It's under immense pressure and there's no oxygen down there.

publiusr
2017-Feb-17, 09:38 PM
Maybe those were the carbon units V'ger was really talking about...

Ara Pacis
2017-Feb-18, 05:27 AM
IFLS says it's carbonate: http://www.iflscience.com/environment/seriously-weird-beneath-yellowstone/all/

Swift
2017-Feb-18, 03:11 PM
IFLS says it's carbonate: http://www.iflscience.com/environment/seriously-weird-beneath-yellowstone/all/
Nice find


There's no "H" in the formula though.
The hydrogen could be in there either as water (you can have some water in melts) or as molten bicarbonates (HCO3-)

Squink
2017-Feb-18, 07:54 PM
Carbonatite (Na + K Carbionates) lava at 510 C from Ol Doinyo Lengai volcano (https://en.wikipedia.org/wiki/Ol_Doinyo_Lengai) in Tanzania.

kzb
2017-Feb-19, 04:38 PM
Nice find


The hydrogen could be in there either as water (you can have some water in melts) or as molten bicarbonates (HCO3-)

Fair enough. I don't understand how neutral carbonate salts would affect the climate though.

publiusr
2017-Feb-24, 10:25 PM
So..what does this mean for geothermal power--more do-able perhaps?

Grey
2017-Feb-25, 02:56 PM
So..what does this mean for geothermal power--more do-able perhaps?It's 350 km below the surface. I can't imagine there would by any practical way to use this for geothermal power.

BigDon
2017-Mar-17, 06:06 PM
It's 350 km below the surface. I can't imagine there would by any practical way to use this for geothermal power.

Not like we need a new source.

We don't even use all the geothermal we do have access to properly. I know of two places, Iceland and California where it's used to supply more than token amounts of power. (Token = less than 500 people.)

Squink
2017-Mar-21, 02:54 AM
Iceland and CaliforniaPossibly Nevada (https://lasvegassun.com/news/2015/mar/16/nevada-hotbed-geothermal-activity/)
As of 2013, there were 29 operating geothermal power plants in Nevada producing 518 megawatts of electricity. Idaho appears to have hit a wall (http://snakeriveralliance.org/what-happened-to-idahos-geothermal-ken-miller/).

Can't forget New Zealand (https://en.wikipedia.org/wiki/Geothermal_power_in_New_Zealand).
Geothermal power in New Zealand is a small but significant part of the energy generation capacity of the country, providing approximately 13% of the country's electricity[1] with installed capacity of 854 MW

China may even be getting somewhere, despite the unfortunate choice of headlines: China will boost geothermal energy development over the next 5 years (http://www.thinkgeoenergy.com/china-will-boost-geothermal-energy-development-over-the-next-5-years/)

Jens
2017-Mar-21, 05:59 AM
Sounds nice for a warm winter swim. :)