ClimateCooling via Plate Tectonics?

[exchemist]

Interesting article in today's Indie: https://www.independent.co.uk/news/...ty-earth-climate-change-co2-mit-a8822711.html

MIT seems to have published some research correlating the onset of various ice ages with the upthrust of oceanic crust that often accompanies the closure of oceans. The idea seems to be that the chemical composition of oceanic crust includes rocks that absorb CO2 from the atmosphere.

I vaguely recall the old distinction between "sial" and "sima", viz. Si/Al vs. Si/Mg that distinguishes the two. However I don't have any detailed information on the mineralogy of these rocks. I can certainly see that Mg has a propensity to form carbonates, but what the thermodynamics is of Mg carbonates vs. various complex Mg silicates I do not know.

Does anyone have access to the paper? I'd be interested to read it.

 

[sculptor]

Interesting hypothesis.
Reading more now.
Thanx

 

[sculptor]

OK from what I've read, I ain't buying it.

 

[James R]

OK from what I've read, I ain't buying it.

Maybe a link to what you read might help.... (?)

 

[exchemist]

OK from what I've read, I ain't buying it.

What makes you sceptical? As I say, it seems plausible that some lower crustal rocks could have a chemistry that makes them capable of producing carbonates on exposure to CO2. But I would like to see what these minerals are and what chemical reactions they hypothesise.

 

[Yazata]

MIT seems to have published some research correlating the onset of various ice ages with the upthrust of oceanic crust that often accompanies the closure of oceans...

Does anyone have access to the paper? I'd be interested to read it.

Apparently the paper is published in Science. The latest Mar 15 issue seems to be a special issue on pediatric cancer, so this paper may not be published yet, just submitted and accepted. (Dunno if it will be behind a paywall.)

http://science.sciencemag.org/

This isn't the actual paper, but it's an unusually detailed press release from MIT's Earth, Atmosphere and Planetary Science dept. (I think that it's what the news stories are based on):

https://eapsweb.mit.edu/news/2019/tectonics-tropics-trigger-earths-ice-ages-study-finds

This isn't the paper that you are referring to either, but it says something similar and seemingly related. It's U. of Texas researchers suggesting that the onset of plate tectonics might have come relatively late in the Earth's history and is what triggered the 'snowball Earth' episodes.

https://onlinelibrary.wiley.com/doi/full/10.1111/ter.12321

 

[exchemist]

Apparently the paper is published in Science. The latest Mar 15 issue seems to be a special issue on pediatric cancer, so this paper may not be published yet, just submitted and accepted. (Dunno if it will be behind a paywall.)

http://science.sciencemag.org/

This isn't the actual paper, but it's an unusually detailed press release from MIT's Earth, Atmosphere and Planetary Science dept. (I think that it's what the news stories are based on):

https://eapsweb.mit.edu/news/2019/tectonics-tropics-trigger-earths-ice-ages-study-finds

This isn't the paper that you are referring to either, but it says something similar and seemingly related. It's U. of Texas researchers suggesting that the onset of plate tectonics might have come relatively late in the Earth's history and is what triggered the 'snowball Earth' episodes.

https://onlinelibrary.wiley.com/doi/full/10.1111/ter.12321

Thanks for this. These links of yours have led me to two more which I think shed a lot of light on the topic:

This one: https://www.whoi.edu/fileserver.do?id=142265&pt=2&p=86851 refers to a study of ophiolites in Oman that have been chemically altered to carbonate-rich minerals. The authors are interested in the potential for such rocks to lock up atmospheric carbon in carbon capture processes.

This one: https://en.wikipedia.org/wiki/Serpentinite. describes the chemical weathering process by which peridotites, and olivine in particular, can be chemically weathered, either by water into serpentinite or by CO2. Reaction 2b is the answer to my original question. So, what I've learned from all this is that indeed anhydrous ultramafic minerals from the mantle, when exposed at the surface, are unstable. They react comparatively readily with both water and CO2, in the latter case forming magnesium and calcium carbonates.

It seems to me that the MIT study, while suggestive, is far from conclusive that this process could have ushered in the ice ages. For a start, do we have evidence that atmospheric CO2 was lower during the ice ages? And if we do have such evidence, how can we establish the CO2-weathering of these rocks could compete with weathering by water enough to mop up significant amounts of atmospheric CO2? The MIT report does not seem to address these questions, at least, not according to the abstract.

 

[iceaura]

For a start, do we have evidence that atmospheric CO2 was lower during the ice ages? And if we do have such evidence, how can we establish the CO2-weathering of these rocks could compete with weathering by water enough to mop up significant amounts of atmospheric CO2?

http://www.johnenglander.net/chart-of-420000-year-history-temperature-co2-sea-level/
-
There's evidence that partial pressure of oxygen (atmospheric density in general) makes a difference in the warming effects of CO2 - the absolute levels of CO2 are not one-one correlated with warming regardless of the rest of the atmosphere. A reference I can no longer track down easily, from a couple years back, had graphs and stuff, concluded that high O2 levels accounted for some of the anomalies in the the paleontological CO2/Temp correlations. You may have better luck.
-
Rock weathering by water and weathering by CO2 are largely the same thing - if Wiki is good enough:

- - When exposed to air, silicate rocks undergo weathering reactions which remove carbon dioxide from the atmosphere. These reactions proceed in the general form: Rock-forming mineral + CO2 + H2O → cations + bicarbonate + SiO2. An example of such a reaction is the weathering of wollastonite:
CaSiO3 + 2CO2 + H2O → Ca2+ + SiO2 + 2HCO3−
The released calcium cations react with the dissolved bicarbonate in the ocean to form calcium carbonate as a chemically precipitated sedimentary rock.

 

[exchemist]

http://www.johnenglander.net/chart-of-420000-year-history-temperature-co2-sea-level/
-
There's evidence that partial pressure of oxygen (atmospheric density in general) makes a difference in the warming effects of CO2 - the absolute levels of CO2 are not one-one correlated with warming regardless of the rest of the atmosphere. A reference I can no longer track down easily, from a couple years back, had graphs and stuff, concluded that high O2 levels accounted for some of the anomalies in the the paleontological CO2/Temp correlations. You may have better luck.
-
Rock weathering by water and weathering by CO2 are largely the same thing - if Wiki is good enough:

Very interesting indeed. Thanks for this. The graphs certainly show a strong correlation between fluctuations in CO2 and temperature. So that answers my first question. The effect of O2 is interesting and it is not immediately obvious one would expect that, certainly.

 

[sculptor]

Maybe a link to what you read might help.... (?)

Yeh
Oops
..............
(often, when researching, i will open many places wherein i perceive that i might find answers to the current question----------many are dead ends, some offer different information which create different questions which lead to opening more places wherein i might find answers which may lead to different information...............etc...-repeat)
eg
something about the claim that the contact point of india/asia being in the tropics, created a discomfort when applying the new information to extant memory---ergo more reading---it seems most likely that the contact/suture point was actually in the sub-tropics---by a degree or two (or more)......................
.ok. small problem.....
then when did india leave it's neighbors in gondwana---and then to evolution of marsupials---again we have things that need far more research---india has been hypothesized to have left gondwana before the evolution of marsupials---however, we have marsupial fossils in india and in mongolia-(HUH WUT?)---
again this begs for more research---and then, we have the potential for sidetracks like your friendly neighborhood Thylacosmilus-(very interesting fellow)----

What I've listed here is just the tip of the iceberg(so to speak).

long before i'm done, the computer has slowed to something approximating a dead stop with all the open windows, tabs, and threads
so i close many of the previously opened threads and windows en masse with nary a backward glance

Which, my apologies, makes honoring your request exceedingly difficult.
Oops

 

[sculptor]

OK
kicking the can down the road
Dan Britt also thinks that India crashing into Asia caused this current ice age
here's a link to his video----look 19-20 minutes into it for that connection

.....................
Ok this was done before the Lake El’gygytgyn data was published---so some is based on old views without the knowledge of "super-interglacials".