What about mantle plumes?

[Travis]

I'll admit that I find the idea of mantle plumes driving tectonics to be quite interesting. And I love this place www.mantleplumes.org because I can go through journal manuscripts for free.

So does anyone have any knowledge to share? I know we have some geologists here. Are they real? Are they the driving force for tectonics and rifting? Just how prevalent are large igneous provinces?



Oh, and I know this is kinda out of nowhere, but is there any indication where the next huge flood basalt eruption might take place?

Rift valley in Africa maybe?

 

[Pulvinar]

Oh, and I know this is kinda out of nowhere, but is there any indication where the next huge flood basalt eruption might take place?

That's been keeping me up nights worrying too.

 

[Travis]

Humankind has never witnessed one to my knowledge. Think of what we could learn!

 

[dlorde]

Humankind has never witnessed one to my knowledge. Think of what we could learn!

We might not last long enough to use the knowledge - such an eruption was a good alternative candidate for the extinction of the dinosaurs, and in any case, made a significant contribution. See Deccan Traps.

 

[Correa Neto]

Wanna see plume-induced volcanism? Go visit Iceland or Hawai. At those islands, you'll get a pretty good view of how the past LIPs (Large Igneous Provinces) should have looked like, since they are basaltic LIPs.
Plume tectonics is OK, conventional plate tectonis is OK too. It all depends on where and when you are looking at on Earth. Some major plume episodes (usually associated to supercontinent break-up) seem to hapen every now and then across geological time. You would have (if this idea is correct) periods dominated by Wilson cycles-style tectonics and periods of more vigorous activity, dominated by plume tectonics. Since Earth was hotter in the past, some say plume tectonics was more common untill about 1.8Gy ago or so.

As a sidenote, I have my share of doubts about the Deccan Trapps as a major factor on the extinction of dinosaurs & Co. They survived the Parana-Etendeka LIP associated with Gondwana break-up, after all. As an environmental stress factor, yes. As a major contributer, my guess is no (note the word "guess").

This put, I'll return to my cozy Paleoproterozoic and Neoarchean times...

 

[Dymanic]

I'll admit that I find the idea of mantle plumes driving tectonics to be quite interesting.

Are they real? Are they the driving force for tectonics and rifting?

These questions seem to be rather widely perceived as having been long settled. It's nice to see some awareness that not all geologists share that confidence.

 

[AlBell]

Humankind has never witnessed one to my knowledge.

Dodged that bullet so far anyway.

Think of what we could learn!

People need to learn how to die? I think not.

 

[Correa Neto]

Geology is a science. Being a science, it evolves, it is improved as any science is supposed to do. Mantle plumes and mantle avalanches IIRC were new stuff around the early 90's or late 80's. Plate tectonics theory has then being improved with the addition of plumes'roles and their links with LIPs and supercontinent break-up episodes. Their role was also recognized in metallogenesis (they can account for certain periods in geological time which are known for the abundance of a given type of mineralisation) and stratigraphy (there's a link between major global transgressions -events of elevated sea levels- and plume activity at mid-oceanic ridges).

By the way, if someone is wondering, the answer is no. Plume tectonics by no means makes stuff like YEC, expanding Earth and Atlantis more plausible.

 

[Dymanic]

Geology is a science. Being a science, it evolves, it is improved as any science is supposed to do.

And the process can be painful. And ugly. Rifts often develop (so to speak) between adherents to various explanations for an observed phenomenon, and the discourse, which sometimes becomes surprisingly unfriendly, is rather prone to spilling over into less "pure" areas of human endeavor such as politics and economics (though, to be sure, it's easy enough to become attached to a particularly elegant explanation -- and reluctant to relinquish it -- even before all of that other stuff comes into play).

Textbooks must be printed, after all, and professional careers begin with mastery of the concepts contained in those textbooks; so a challenge to those concepts may be perceived by some as an indirect challenge to their authority as experts. Depending on how much of their professional status they have staked on the validity of those concepts, some may go to great lengths to defend them even when doing so requires coming up with an increasingly clumsy series of patches and workarounds. So if, for example, seismic tomography fails to confirm the existence of the large convection cells predicted by earlier theory (which it has failed to do), some may adjust to that disappointing result more easily than others, and the reasons may not necessarily be based entirely on the science.

I can't disagree that evolving and improving is what science is "supposed to do", and I accept that it mostly manages to accomplish that (eventually, anyway). But any naive notions I might ever have had about it being anything but a high-stakes game of one-upmanship were shattered long ago. When I followed the dialogue between two of the men I long regarded as among the leading thinkers of our time, Richard Dawkins and Stephen Gould, and watched that exchange become increasingly vicious and personal, I felt like a little kid lying in bed listening to his parents fight.

It may well be that the gorilla genome is improved by having breeding opportunities preferentially go to those males most adept at chest-thumping, but I don't see there necessarily being any guarantee of that, and in any case, improving the genome surely isn't what motivates them to do it.

 

[Dinwar]

such an eruption was a good alternative candidate for the extinction of the dinosaurs, and in any case, made a significant contribution. See Deccan Traps.

It's not as popular a theory any more. Gerta Keller is the name you want to look up when it comes to this, by the way. I heard her give a talk a few years back. Very, very detailed, but fairly controversial, even for K/Pg talks.

And I should emphasize one point: dinosaurs DID NOT go extinct. In fact, my wife ate one for supper. This is neither trivial nor facetious: we cannot talk about THE extinction of THE dinosaurs because they're still with us.

If you want my $0.02, the K/Pg event, like any mass extinction (turn-over or die-off type) was the result of a number of things happening in a relatively short period of time. I mean, we know that a bolide hit Chixilub. We know that numerous others hit the plant around that time. We know that the Deccan Traps went off. Asking which one "caused" the mass extinction is like asking which bullet killed Scarface--it doesn't really matter, and it's a completely fictitious way to look at the situation.

Dymanic, I have to ask: Was there a point to your second post other than to complain about how geology gets done? As someone who's involved in a professional disagreement or two myself I can attest to the fact that the science isn't always as central to the arguments as it should be; that said, what separates science from a schoolyard is that science has rules. Both sides are required to present evidence, for example. So while it can sometimes get personal (and if you're extrapolating from Gould and Dawkins you're missing a few golden opportunities to make your case, particularly in geology--we've always been a rough-and-tumble lot), there's a limit.

Second, if anyone gets their understanding of any science only from the celebrities (particularly celebrities that aren't in the field--Dawkins is a biologist, not a paleontologist, and the two fields are separate for reasons, some good, some not so much) I strongly believe they should re-assess how well they really understand that field. The best science isn't done by the celebrities. It's done by people like H. Milne Edwards, or Eric Scott, or Dibblee--people who's names aren't household words for the general public, but they certainly are for the professionals (I defy anyone to do Southern California geology without using a Dibblee map, for example).

So yeah, sometimes egos get in the way. Sometimes it gets rather ugly--and it gets a LOT uglier than a few heated words exchanged, believe me. But the beauty of science is that it can work despite all of that.

 

[Dymanic]

Dymanic, I have to ask: Was there a point to your second post other than to complain about how geology gets done?

Is there a point to any of what we do here?

 

[Dinwar]

Well, it's just that while a discussion of what happens when egos clash is interesting and certainly worth its own thread, it really doesn't have much to do with mantel plumes. Neither Dawkins nor Gould knew enough about the topic to discuss it, and the issue of mantel plumes is certainly not answered (my wife worked with a professor who studied the idea, for example). I'm just saying that it seemed like it's a bit of a tangent, and a very tenuous one.

 

[Skeptic Ginger]

I find the basalt floods fascinating as I've seen the evidence of such magma floods nearby. You can't help but be awed at the magma flood when you see the evidence.

And Yellowstone is a fantastic place to visit. I keep an eye on the quake activity at Mammoth Lakes. It's more active than Yellowstone as far as quake activity goes.

Interesting link, thanks.

 

[Dymanic]

Well, it's just that while a discussion of what happens when egos clash is interesting and certainly worth its own thread, it really doesn't have much to do with mantel plumes. Neither Dawkins nor Gould knew enough about the topic to discuss it, and the issue of mantel plumes is certainly not answered (my wife worked with a professor who studied the idea, for example). I'm just saying that it seemed like it's a bit of a tangent, and a very tenuous one.

That anecdote went to the issue of "what science is supposed to do". Geology, being a science, IS evolving and improving, and I certainly won't deny it. I might propose that clashing egos are THE driving mechanism behind that, but to phrase it that way would be to implicitly minimize or even dismiss other forces that might exert just as strong an influence, and, if you really look at it, the "clashing egos" hypothesis isn't actually necessary to explain the phenomenon at all.

No, the issue of mantle plumes is not answered, but a lot of folks appear not to have gotten the memo. Ask, "What is the driving force behind plate tectonics?" and they'll respond, "Why, just go to Iceland and you can see it with your own eyes".

I mean, that may very well be true, but let's do take note of the fact that this whole "plume" business is still a theoretical construct; one which, at the very least, may turn out to have been somewhat over-applied. If that does turn out to be the case, it seems quite relevant to consider how the idea came to be so widely embraced in the first place if there never was much hard evidence to support it.

 

[Dinwar]

No, the issue of mantle plumes is not answered, but a lot of folks appear not to have gotten the memo. Ask, "What is the driving force behind plate tectonics?" and they'll respond, "Why, just go to Iceland and you can see it with your own eyes".

Which folks are you talking to?

If you're talking to the man on the street, it's irrelevant. They get their opinions from The History Channel and The Discovery Channel.

If you're talking to geologists, I imagine that's their way of saying "I've got better things to do than discuss plate tectonics just now". I mean, it'd be pretty stupid of a geologist to say that and actually mean it--hot-spot volcanism more or less disproves the idea that convection cells drive all of it. They also could be referring to the ridge-push effect, which is one of the mechanisms that drives most tectonic activity.

Really, unless you were talking to a geophycisist who was studying tectonics, the answer you get is largely irrelevant. It'll either be a brush-off, or an uninformed opinion.

If that does turn out to be the case, it seems quite relevant to consider how the idea came to be so widely embraced in the first place if there never was much hard evidence to support it.

Check out the history of geology sometime. We have a rather ignoble history of popularizing theories with little factual support. It's pretty easy to do in a science that often has only one or two datapoints to work with.

ETA:

I might propose that clashing egos are THE driving mechanism behind that,

Simply put, you would be completely wrong. It may be the driving force behind the big, popular, sexy theories, but the driving force behind science is the methodical work of people who's names you'll never know, and who generally get along with their colleagues. Far more often than not, data are what sway the opinions of scientists. You just never hear about it because people going "Huh, I was wrong" doesn't make the news.

 

[volcano]

I'll admit that I find the idea of mantle plumes driving tectonics to be quite interesting. And I love this place www.mantleplumes.org because I can go through journal manuscripts for free.

So does anyone have any knowledge to share? I know we have some geologists here. Are they real? Are they the driving force for tectonics and rifting? Just how prevalent are large igneous provinces?



Oh, and I know this is kinda out of nowhere, but is there any indication where the next huge flood basalt eruption might take place?

Rift valley in Africa maybe?

The folks that run mantleplumes.org have made a serious attempt to make it look like a website that explores both sides of "the controversy"-- but in reality, their ideas deviate somewhat from the mainstream and garner many rolled eyes in the community (and occasionally even hushed giggles at conferences). The website does post articles from scientists with competing, but more widely-accepted theories, though, so it can be useful place to find manuscripts-- but only SOME of the manuscripts are presenting well-supported mainstream science.

When the plume model was first developed (Morgan, 1972), it explained a lot of previously-unexplained observations (age progression in island chains like Hawaii and Galapagos, for example). Like any newly-developed "unified theory," the tendency was to use it to explain EVERYTHING that was previously unexplained. "We don't know why these island are here." "Must be a mantle plume!" and the theory was probably somewhat over-applied. But the mantleplumes.org folks reacted in the opposite direction, and said "Plumes don't exist AT ALL!" They explain the age progression of certain island chains are crack propagation through the crust, which requires a ton of other factors for which we have no evidence. In many places, the plume model works, and it works well.

As for plate tectonics-- mantle plumes like the ones at Iceland and Galapagos and Hawaii aren't generally considered the main driver of plate tectonics. Mantle convection currents, which are much larger than plumes (we think-- the imaging of these things isn't great yet!), probably drive plate tectonics. Mantle convection drives upwelling at mid-ocean ridges and downwelling at subduction zones. Plate tectonics might be driven by upwelling at mid-ocean ridges, it might be "slab pull" from the momentum of the down-going subducted plate, it might be (and probably is) a combination of both.

And one final note-- large igneous provinces (LIPs) are a somewhat special beast of mantle plume, more akin to "superplumes." They're rare in the geological record, but explain enormous-scale eruptions like the Columbia River Flood Basalts and the Deccan Traps, which I believe are inadequately explained by the ideas presented at mantleplumes.org.

For once, there's a topic on JREF about which I consider myself relatively well-informed, and I'm happy to provide additional references, links, etc. if that would contribute to this discussion

 

[Dymanic]

Which folks are you talking to?

If you're talking to the man on the street, it's irrelevant. They get their opinions from The History Channel and The Discovery Channel.

If I'm lucky. A disturbing number of them appear to get most of their opinions from FOX "News" and the like, and attempting to discuss much of anything with them is generally a waste of time. The folks with whom I spend most of my time talking about this sort of thing (other than one of my kids who is near to earning a degree in geology) are here on JREF.

Really, unless you were talking to a geophycisist who was studying tectonics, the answer you get is largely irrelevant. It'll either be a brush-off, or an uninformed opinion.

So, to answer my own question above, the point of what we do here is expressed by the "E" in "JREF".

Check out the history of geology sometime. We have a rather ignoble history of popularizing theories with little factual support. It's pretty easy to do in a science that often has only one or two datapoints to work with.

That this is largely the case with regard to mantle plumes was precisely the point I was making.

Simply put, you would be completely wrong.

Or at least possibly mostly wrong, which, again, was precisely my point. I assume that you read the rest of that rather lengthy sentence, but you appear to have missed the fact that I was using it as an analogy for the way the "plume" hypothesis has gained a degree of traction it may not deserve.

 

[Dymanic]

The folks that run mantleplumes.org have made a serious attempt to make it look like a website that explores both sides of "the controversy"

I think it mostly represents the viewpoint of a single individual, Gillian R. Foulger, Professor of Geophysics at Durham University, and relies a lot on material appearing in her book, "Plates Versus Plumes, A Geological Controversy. I haven't read it, but one of the reviewers, Professor J. Godfrey Fitton, Professor of Igneous Petrology at the University of Edinburgh, had this to say as far as the "both sides of the controversy" issue goes:

"The title of this book might lead one to expect a balanced review of the current mantle plume controversy, but it isn’t and it doesn’t claim to be one. Instead it is an eloquent polemic against the plume hypothesis written by someone who genuinely can see no merit in it and is passionate in her opposition to it. The reader should bear this in mind. Professor Foulger starts from the position that the plume concept has been so stretched to accommodate all mantle melting anomalies that it is by now untestable and therefore unfalsifiable, and that the term plume is ‘so often used for convenience that the difference between a label and an explanation has become lost’. In this she is undoubtedly correct. Her thesis is that all melting anomalies, intraplate (e.g. Hawaii) or on spreading centres (e.g. Iceland), can be explained by shallow plate tectonic processes without recourse to hot, buoyant plumes rising from the deep mantle. In this she is, in my view, almost certainly wrong."

 

[Correa Neto]

Every time I see someone complaining about egos and science, that egos are ahead of evidence, I also hear alarm bells. No one will deny that ego clashes happen in science, clashes that ideally should not happen. Science is a human entreprise and thus subject to eventual failures generated by human nature. But it seems, from where I am standing, you are overestimating the role of egos and politics. Don't get me wrong, but this is usually something that comes from defenders of fringe subjects, pseudoscience and in the best case some scientific-minded but stubborn folks.

Example- last Friday I was watced three talks on AGW from the folks at the "no" side. Make no mistake, those were top researchers, whose credentials and CVs would humble most people. I will not enter on OT specifics, suffice to say they were showing some rather interesting data, some of which I could understand, since they were well within my field, some other flew way high above my head. Sure, there were issues with their interpretations (the ones I could understand), but they completely lost me when the complaints against politics, dogma et al started. If the data is good, if the interpretation is good, you will not need to resort to whining. The outcome will be good. It might take some time, but it will happen.

Some ideas every now and then are overvalued and overused? Should anyone be surprised? It happens everywhere.

So, someone answered you should go to Iceland and see it. I wish I could. This put, are you sure you asked the right question? Are you sure whoever gave you the answer actually understood your question? "Go to Iceland and see it by yourself" is the (rather sarcastic) answer I would give to someone who does not believe in plate tectonics. YEC or someone aguing for an outdated Beloussov-like theory for example.

Regarding textbooks, they are a pain to write and publish. The odds are by the time you managed to finish writing it, it already has outdated sections. And when at last it is printed, even more stuff will become outdated. Note also they are not easy to update.

Now, if you have something that works better than science, please show it.

And regarding plumes, convection cells, etc., I sugest you to check the relatively recent works on tomography of the Earth as well as more recent works on the driving mechanisms of plate movements. I see Volcano already skimmed the issue (slow typer doing three things at the same time her).

 

[Dinwar]

I assume that you read the rest of that rather lengthy sentence, but you appear to have missed the fact that I was using it as an analogy for the way the "plume" hypothesis has gained a degree of traction it may not deserve.

Yes, I read your statement. What I'm saying is that you're doing exactly what you accuse others of doing: drawing conclusions too firmly based on too little evidence. Clashing egos happen. We're human, and humans don't like to be wrong. That said, science is constructed so that eventually the data WILL win. It may not be as fast as some people would like, but it will happen.

That this is largely the case with regard to mantle plumes was precisely the point I was making.

The fact that we can say that the ideas were not adequately supported is proof that we no longer agree with them, and evidence that the scientific process works. It may not be working fast enough for you in this case, but there's a real simple solution to that: research the topic, and join the debate.

Professor Foulger starts from the position that the plume concept has been so stretched to accommodate all mantle melting anomalies that it is by now untestable and therefore unfalsifiable, and that the term plume is ‘so often used for convenience that the difference between a label and an explanation has become lost’. In this she is undoubtedly correct. Her thesis is that all melting anomalies, intraplate (e.g. Hawaii) or on spreading centres (e.g. Iceland), can be explained by shallow plate tectonic processes without recourse to hot, buoyant plumes rising from the deep mantle. In this she is, in my view, almost certainly wrong."

This is why I love science. Scientists are expected to take ideas and see if they work, in part or as a whole. If the whole doesn't work but some parts do, we keep the parts that do and discard the rest. Okay, yeah, the author of that book may be overstating her case--but that doesn't mean that the book is entirely without value. This is somewhat unique in human endeavors--most will discard the things wholesale.