Sorry about the lack of posts - I've been not only frantically prepping for class and my Eyja talk, but also I'm somewhat under the weather with an ill-timed sickness, so even though there is stuff to talk about, I haven't really had time/wherewithal to deal with it.
However, expect big things from Eruptions next week!
Drawing of a ship washed inland by the tsunami generated by the August 27, 1883 eruption of Krakatau.
I'll throw a few quick links:
- The alert status at Galeras has been dropped back down to "orange" after the non-explosive eruption earlier this week. However, INGEOMINAS warns us the threat is still there (spanish) for an eruption (and more evacuations).
- Another volcano anniversary falls this week - this time the 1883 eruption of Krakatau in Indonesia. You can even hear a witness to the actual eruption get interviewed by author Simon Winchester.
- Curious about what is going on underneath Yellowstone - check out the great post on Highly Allochthonous that examines the source of the giant North American caldera system.
- Dr. Boris Behncke has kept us appraised on the currently activity at Etna on his photostream - not a lot of coverage of this new activity at the Italian volcano in any other media source.
- And you can catch up on all the week's volcano news with the Global Volcanism Program's Weekly Volcanic Activity Report!
Eruptions readers who recall our technical chitchat here on deep focal earthquakes,
you will very much want to go look at Chris Rowan's blog entry for today, mentioned in Erics opener above.
Look closely at Fig 2B. What do we see?
We see what looks very much like a critical folding unit dimension of 200 Km.
The twisting corkscrew shape that Chris mentions is a massive torsional movement that is mirrored in the curving path of the hotspot, seen in the first blog figure.
I am thinking that we are seeing an interesting phenomenon:
The 'unpleating' of the folded subducted crust.
Recent tomography evidence of PNW crust subduction through deep focus EQ modeling (discussed in papers I presented in July, linked above) suggests that diving crust remains intact - stretched and thinned, but with structural integrity in place, as it descends to just below 800 Km.
So, I'm not what happens as it's mashed down into pleated folds, but it sure does look like it's a pleated and unfolding structure that is feeding upwards as the Yellowstone hot spot.
Now, with this picture in mind, look at the last set of modeled tomographic data. See the cold subducting crust plunge downward at the coast, being pleated and stacked at some critical depth (S2), and then an ancient fragment rising by convection, to emerge below and along the path of the Yellowstone hotspot?
Could be coincidence (the apparent pleated geometry), but if this is true, it's quite remarkable!
We cannot be too grateful for your relentless endeavor in keeping us updated with all kinds of geological information whatsoever. This your blog is an outstanding example of generosity in sharing knowledge and arousing curiosity as a mean of improving our understanding of the world and the relationships between man, science and Nature.
And I also want to thank Boris, ECho and all the other collaborators, as well as our fellow bloggers who, with their valuable comments and posts contribute to keep this blog "rocking". It's been a thrilling experience to be around.
I must confess I'm still far from grasping the whole picture in which concerns magma and volcanoes, but I'm fascinated and eager to learn more.
I'm specially interested in understanding the mechanisms governing plate tectonics and hotspots. Although my expertise is yet insufficient to go deep into the matter, I daresay that, concerning the mantle plume theory, there must be some kind of gap between what is being explained and what is really taking place underneath. Except for Hawaii, where mantle plume provides a very plausible explanation for volcanism, there must be a link between sinking of old plates and hotspots elsewhere. We've seen that kind of connection in Iceland and Yellowstone and recent EQ activity in ancient subduction zones appear as good examples of weird behaviors of magma formation.
It has been said recently in this blog that the mantleplume.org would be a questionable source, though the article in Highly Allochthonous points to the site.
Maybe you could give us some opinion about this as well as some other reliable sources in the net (or books) where a layman like me could get a good perspective in the actual course of debate.
Many thanks in advance.
As soon as I have sent my last post I saw your comment on Chris Rowan's blog. I must give you a special thank for getting me into this debate and for the whole lot of fascinating homeworking you have been charging me with. I can already feel the good results, so I hope. :)
Renato, meet Dr. Foulger:
I used her consulting cv, as it's more up-to-date than her faculty 'vita. She's certainly legit and so is her website.
Ah, the dreaded late-summer ick. Hope it clears your system soon!
I was thinking of buying the book, but I was afraid it would be too difficult to my present level, but since you recommend it, I'll give it a try. Many thanks.
Renato, I wasn't referring to her book, but to her website, in reply to your post query.
If you are thinking about trying her book, you should write to Dr Foulger and ask if it's appropriate for the general public. At the very least, you should work through the material on her mantle.org website.
Yes, that is exactly what I needed when I addressed to Erik. I didn't notice the contents before I answered to your post. Cool! After going through the site I might as well be able to understand the book.
Oh, dear, and all my daily errands waiting for me...
Look what you've done to me! ;)
Just found what I wanted here: The Mantle Plume Hypothesis Pro and Con: Evidence from Earth's Most Voluminous Large Igneous Provinces.
"A common mechanism for the formation of LIPs is highly desirable, yet, at present, all existing hypotheses appear in some way deficient."
Yes. That's exactly what I meant, but to go deeper in the matter I'll have to wait till I have enough time to grasp the basics on seismology and petrology.
As they say in Italian: Piano, piano, si va lontano.
Start at the simple level and then move into Gillian's website, with a range of factual complexity.
www.rasmussen.edu/student-life/blogs/main/beginners-guide-to-plate-tect… (NASA recommended)
USGS, This Dynamic Earth - The Story of Plate Tectonics (online edition)
Introduction to Plate Tectonics
Virtual Upper Mantle
Geology.com earth internal structure
As they say in Italian (musical direction): poco a poco.
More recent mantle plume theory and discussion, Episodes, March 2007 (several papers, start with Dr Xu's intro)
Since the Episodes volume 30 March issue mentions the OneGeology concept, introduced in 2007, I'll throw in the link to this global geology website.
#13 Grazie infinite!
What an invaluable material!
All links are bookmarked and I'll take the weekend to start studying them "poco a poco" (actually, I've already started).
Now I'd like to repost a link to this RUV article. Do you have any idea of what could they be? Cracks being found along the Icelandic rift system?
"New cracks in Sprengisandur"
Thank you very much.
If I remember correctly you where the one *snorting* the most about my little brain-fast of the vorticing plumes/hotspots. I find it hilarious that you a few weeks later present the only "proof" of that idea so far. If I remember you even went to the trouble to suggest I should study fluid dynamics before saying anything... Haha!
The world is a small thing after all:)
@Renato: The geophysicist PÃ¡ll Einarsson thinks these cracks, brand new as they are, are somehow related to the eruption in VatnajÃ¶kull glacier in 1996.
Renato, the cranks are in the Highlands between HofsjÃ¶kull and VatnajÃ¶kull icecaps. It's a dry volcanic and gravel flood deposit plain. They're associated with area rift systems, and their appearance in Spring and Summer suggests erosional exposure at the surface from glacier melt floods.
If Pall Einarsson infers that they're related to the Gjalp 1996 eruption, he might be referring to crustal deformation effects of this event.
Crustal deformation associated with the 1996 GjÃ¡lp subglacial eruption, Iceland: InSAR studies in affected areas adjacent to the VatnajÃ¶kull ice cap, Iceland (2007).
See Figs 1, area 'T' (the rift system mentioned in the riv article), and 2 (interferograms, deformation maps). It's in the approximate area of the cracks reported a few days ago.
Article in English, I found this while reading the Icelandic news on recently formed melt lake to the West on the Ok glacier remnant, posted by birdseye.
I enjoyed very much all your talking about magma fluid behavior. Ever since then, I've been noticing that all plots and graphs concerning quakes distribution and lithosphere deformation, as well as rising magmas, exhibit a cork screw / semi helical pattern. Of course, there are many forces at stake here and we don't know exactly how the stuff in the mantle behaves, whether fluid-like or semi-solid, to state precisely if they go "by the book" in either way. But since we are no experts, we're entitled to do some speculation in this non academic forum and get ready for the criticism. I'm too far from giving my own opinion, but trying to gather some information on this.
What I've read so far draws me back from mantle plume and convection currents theories as being the main responsible for plate movement and magma formation and that gravity is still very much to be blamed. But this is a mere intuition on my part and I'm ready to be slapped on my face to be saying such a sacrilege. Passerby is helping us a lot with all the material he has been providing and I hope someday I'll be able to discuss the subject in a less amateur way. So, let him snort at his leisure. He has already showed he's ready to respond to the good discussion, as you can see in the deep EQ debate.
Love you guys!
#17 #18 @Reynir @Passerby
Thanks for your posts and links. When I read about these cracks I thought they would cast some light in our Icelandic debates, and wanted you guys to examine the finding. I'll take a look at the articles.
#20 I read the article. The crevasses provide evidence supporting Einarsson's hypothesis of slip faulting at TungnafellsjÃ¶kull area due to a 5.6 EQ under Bardarbunga and the 96 Gjalp eruption. Wonder if recent EQ activity to the N of Bardarbunga is anyhow related to this and since activity in the area is somewhat "enigmatic", as they say, we don't know exactly what to expect. The ice sheet there is too thick to give us precise GPS measurements and even to surely state if an eruption has occurred.
The authors do a nice job of presenting possible explanations for deformation and then examining data in light of each case.
You asked for an explanation of the crevasse formation at this location, and since you posted an article quoting Einarsson's comments point to the 1996 eruption, I did the best I could to point to published study connecting cause and effect.
The authors noted deformation to the north as well as the NW. We have already discussed the potential for tectonic faulting absent of intrusions in some locations, and magmetic dike intrusions in others, to explain earthquakes covering a large area to the east of Askja, with many excellent plots provided by Lurking.
so in summary, what goes down must come up?
@Passerby, Renato Rio, Reynir, NK
I have no clue where "Goose Lake" or "New Valley" are at.
Following along, the best I can come up with is the general region between VatnajÃ¶kull and HofsjÃ¶kull.
So, in response to Renato Rio's musing:
"Wonder if recent EQ activity to the N of Bardarbunga is anyhow related to this and since activity in the area is somewhat "enigmatic", as they say, we don't know exactly what to expect."
A plot of this area and recent activity (since 8/1/2010)
I won't be doing many of these plots, I had to layer the quakes in level by level to get them on the background image.
Provided that I got the extents of the background image right.
(the lat and lon of the quakes are accurate)
If Renato will go to Fig. 1 of the 2007 paper cited above, he will see a reasonable match between recent seismic activity and that recorded between Sept 29 and Oct 13, 1996, predating the eruption.
That should answer your last question, RR.
For those of you who think I'm an idiot. Well, your partially correct. But lacking a way of editing my hose ups... I am a fully exposed idiot. Can't zip the fly.
@Renato Rio, etal.
Speaking of Gillian Foulger and plumes, this link may be of interest. I site-searched the scienceblogs.com blog and didn't see it anywhere already.
GÃ¦savÃ¶tn (Goose Lakes): 64Â°46.7'N, 17Â°31'W.
NÃ½idalur (New Valley): The mouth is at ca. 64Â°43'N,18Â°03'W. The valley was first found for certain ca. mid-19th century, hence the name.
Both are popular rest spots after a day of bouncing and jouncing on a fourby trail.
From the www.icelandreview.com link in Passerby's post 
"The crevasses are located a stoneâs throw away from the road between the GaesavÃ¶tn lakes and NÃ½idalur valley. "
And thanks to Reynir, NK's coordinate set on GÃ¦savÃ¶tn and NÃ½idalur, a replot (correctly oriented) with those locations and the background image constraints double checked.
@Renato Rio, all
Please read each of the following books before giving an opinion ...
Haha, just joking. Saw the list and thought of your quest for deeper understanding. Seems like a lot of work.
Famous Quantum Physicist Gerard 't Hooft says any dedicated person, young or old, can become a good PhD-level Quantum Physicist just from free material on the web. The following is a great read regarding acquiring scientific knowledge and expertise on one's on, and also the value of mentors to give guidance (eg passerby).
So it would seem, hopefully, the same would be true of Volcanology.
Here's an animated gif timelapse of yesterday's (Friday) venting from Etna's volcano craters. It is a 4.4 MB file comprised of 95 images taken by CAM 4 8:10 AM to 12:40 PM UTC,
A total of 4 1/2 hrs played back in just a couple of minutes. The images were separated by 2 minutes 40 seonds, which is a limitation given by Cam 3's rate of updating. In this version of the animation, each image is displayed for 200 ms.
The action, like Thursday, started fairly sedated, but built in intensity over time.
Some curious action happens on the edge of the right-most crater .. just barely discernable.
Correction to above: 4 1/2 hours is played back in 20 seconds. So an hour goes by in approximately 4 1/2 seconds!
My dear mentors: I am a mess. I don't think I deserve to be the object of William's experiment on internet learning. Split between sciences and arts, I got stuck on a TV presentation of the last part of "Der Ring des Nibelungen" and missed my errands as well as my geological studies. I'll try to catch up on your recent posts and see what is behind Lurking's plots.
@Passerby: Do you believe we could witness a revival of 1996 around VatnajÃ¶kull any soon? Just caught four more quakes over HerÃ°ubreiÃ° area.
28.08.201023:37:5065.137-16.3965.8 km1.690.014.7 km SSW of HerÃ°ubreiÃ°
28.08.201022:43:2965.090-16.2637.7 km0.535.065.5 km N of Upptyppingar
28.08.201021:58:0965.206-16.3005.2 km1.138.273.6 km WNW of HerÃ°ubreiÃ°arlindir
28.08.201020:34:5264.674-16.5081.1 km1.274.46.7 km NE of KverkfjÃ¶ll
28.08.201020:17:1165.082-16.2687.8 km0.644.654.6 km N of Upptyppingar
#29 @William M Boston: Great link. I ask your permission to quote one paragraph:
"Volcanism that appears to be anomalous (...) results from the inhomogeneity imparted to the mantle by plate tectonics and intraplate deformations that occur preferentially along pre-existing lines of weakness. The possibility of such a radical simplification alone is a strong hint that may something important may be going on here."
That is exactly what we have been discussing isn't it Passerby?
Make sure you understand where you're pointing, to, RR.
We were talking about the clustering under Vatnajokull, NW corner. You're now referring to a fracture zone to the north of the icecap.
If an increase (above interannual average) in geothermal activity under the icecap results in a large lake forming, which is released as a sudden flood, it's possible that volcanic centers (probably Grimsvotn) will be destabilized at either crater or associated fissures and would then erupt. Whether the force of an eruption would be enough to break through 700-900 feet of ice and throw up a large volume of ash, is not known. IES can better address this question.
#37 @Passerby: Yes, I know HerÃ°ubreiÃ° is far to the North of Vatna, but I thought it could be somehow involved in the whole fracture system. But as I see, I am wrong at this.
>That is exactly what we have been discussing isn't it Passerby?
We've discussed interplate EQs, faulting and rifting at sites like Reelfoot Lake/New Madrid fault in the south central US, and to a limited extent, faulting along the Wasatch Front and SW corner of Utah (wrt geothermal activity), but we haven't gone much into intraplate tectonics.
This quote from the same source:
The plume hypothesis as it is applied today requires that Earth dynamics is driven by two independent modes of convection - plate tectonics and plumes. The former is driven by forces at plate boundaries - ridge push and slab pull, and the other is driven by heat from the Earth's core.
is a bit oversimplifed and outdated. That's why I posted a more recent paper written and published a few years ago.
The latter (plumes), especially the mid-depth yellow dots on Courtillot's figure (plumes originating from the depths of the upper mantle) may be a case of intact, less dense folded crust rising with heating from pressure change and mixing chemistry, after passing under thickened continental boundary.
The action of subduction and plume, at least in in the Yellowstone case, does not appear to be 'unrelated'.
What Chris doesn't mention, at Highly Allochthanous, is that there is a physical and very long transverse fault system (with respect to the coast) that roughly parallels (to the south) the A-A' transect shown in Fig 2 of his Yellowstone plume blog post. That's a clue to the curving coastal plate subduction driving the curving torsion, shown in Fig 1.
@38, we have more or less parallel track grouping of EQ activity, but having different mechanisms, as discussed in a couple of nifty papers with referenced figures described here, which Lurking then used to superimpose recent seismic activity for reference, and he also graphed their frequency over time.
#39 When we were discussing the Moro Golf deep focus quakes it was suggested that they have to do with "invisible" subducted plates and related faults, which I understood could be pretty much the same source of meltings under Yellowstone. I apologize for my skipping to conclusions too quickly, and maybe William is right when he tells me to read all those books before I post my opinion (even though he says he was joking). So please feel free to correct me and tell me when I should be quiet. I'm really happy to hear what you guys have to say, but so far I'm convinced that maybe other people could benefit from the wisdom with which you respond to my stupid remarks (yet I could be wrong on this too).
#40 Certainly missed this discussion. My fault.
What intrigues me most is this repeated pattern of swarms (or isolated quakes) occurring almost simultaneously all across Iceland, like over this past 4 hours report from IMO: Reykjanes + Vatna + HerÃ°ubreiÃ° + Askja + TjÃ¶rnes. Difficult to think they are not somehow related (beyond MAR).
Mount Sinabung in Indonesia seems to have had a small eruption today.
If you go to Chris's blog, which started us looking at deep focus earthquakes and possible mechanisms,
He correctly describes the opening sequence of deep focus EQ, that continued for quite a while, as being related
>All four focal mechanisms indicate NW-SE extension. Like the Halmera earthquake, this sequence appears to be linked to the westward subduction of the Philippine plate beneath the Sunda plate, with the earthquakes taking place in a deeply subducted part of the Philippine slab. The extension is probably the result of down dip tension as the slab sinks into the mantle, with the first shock apparently triggering similar events above and below it.
But that only whetted our appetite to know why they are occurring at such depth. While it could be stretching and elongation, the fact that they tend to cluster at specific depths was shown by Lurking in his graph and more obviously, in USGS and PHIVOLCs EQ data that we picked up from a secondary source and couple of related papers.
That made us wonder about the potential for *structure*, because these same critical depths of clustering were found in other places, like near the Cocos plate.
That led to set of references that have, for me, been exciting to read and ponder. For instance, Dr. Courtillot's plume and tectonics map
shows two shallow hot spots, to the east of the subducting Cocos plate, off the coast of Southern Mexico. That could be rising heated and unfolding subducted plate (pleated) that doesn't have the overriding thick continental edge to contend with, so buoyancy, heating convective forces drive it up from shallower depths. Maybe.
Your questions and remarks are never stupid.
Alternate theories - And then there was three.
What we are talking about here, and technical discussions of a few recent papers seem to be pointing to this conclusion, is a third theory: that thinned and subducted plate material sinks into the depths of the upper mantle, much deeper than 400 Km when it's very cold, water-laden ocean material, and is pushed deeply under continental crust, where it, amazingly, remains intact for some distance underneath the lithosphere.
A volcano on Sumatra, named Mount Sinabung stared erupting today at 19:00 GMT (midnight local time). According to news, this is the first eruption in that volcano for 400 years.
Here is the BBC News on this eruption.
Here is the volcano information. But that has last eruption listed as unknown.
Here's a link to the Jakarta Post
Solfataric activity with incandescence 1912, no eruption. Last eruption listed by as 1600AD.
See other related articles, side bar.
Etna popped again
#43 Your last flattering remarks will have me popping up again. Thank you for the incentive, Passerby.
And now, lets learn what is going on in Sumatra.
Thank you for the info, JÃ³n.
And thanks for the update on Etna, Raving.
The statement in nohotspots.htm:
"Seismic imaging around some major, classic hotspots has not found clear evidence of magma conduits below the transition zone (400 to 660 km deep). At the Yellowstone hotspot, Humphreys' team found that the transition zone is cool, not hot."
Seems to be contradicted by the "figure 2" image (right hand side) at all-geo.org/highlyallochthonous/2010/08/yellowstone-what-lies-beneath/
But my real question, if you don't mind:
"...That's a clue to the curving coastal plate subduction driving the curving torsion, shown in Fig 1."
Then what causes the apparent curve? I would think that whatever feature that it cause would trend south ward since the southern edge would be leading the charge. That is unless it separated unevenly.
(Note, I'm not sure where the figure 1 is at, I am assuming it's the image above the labeled "figure 2")
Is it a shearing of the two sides of what once was a spreading center for the Farallon?
You also mention
physical and very long transverse fault system (with respect to the coast) that roughly parallels (to the south) the A-A' transect
Is this a surface feature or a deeper item? If the latter, is it associated with the leftover part of was the spreading center?
According to the 3D model on Wikipedia, the Farallon currently resides deep under the East Coast. You don't happen to think that what is under Yellowstone / Snake River is the left over western part of the Farallon? Sort of the left behind part, all folded up and shoved down into the muck.
Sinabung Simatra erupts after 400 years:
Reuters says 'first eruption in 400 years" -I'd guess they mean "First eruption in at least 400 years" since that's about the length of the historical record there. GVP profile says no confirmed dated eruptions (one uncertain in 1881)
Some of the very first pistures of the eruption on an Indonesian News Site: http://www.google.de/imgres?imgurl=http://www.detiknews.com/images/cont…
@42 (Renato Rio)):
As you know I once sugested that there is a force running all those formations, and that those separate formations where taking there force from one central source of power.
My theory might be glaringly wrong since I am not a geaologist, but mathematically the theory is sound and corroborates with at least some of the evidence witnessed in the simultaneus events we can all see.
About my theory, the basis for my initial thought was to look for inital causes of that part of the world. Because I think we can all agree that something is lacking in the standard modell, my theory might be entirely wrong, but someone has to come up with a theory in the end to fill up the missing parts sooner or later.
And let me remind you that almost all of todays theoris are just theoris. One should always challenge them now and then, even if it is done from someone who is wildly out of his field of expertise. In my case my knowledge of geology is to low (but I do have some and gaining more every day), but my knowledge in physics in general and fluid dynamics in particular is good. If I ever gain enough knowledge about geology I will probably sumarize it into a paper, mostly out of the math being really neat.
What I really would like, is to see an original thought from Passerby on the subject.
Sinabung in North Sumatra is quite close to Toba. It's located close to the town of Berastagi. There is an adjacent Volcano - Sibayak which overshadows the township itself. The two Volcanos maybe plumbing related. Berastagi is an important vegetable and fruit growing area. Its located on a plateau around 1000 metres above sea level - The temperature there is very pleasant.
Here are some images.
This is Sinabung. Note that there have been sulpheric emissions for hundreds of years.
Here's its sister Sibayak
More about Sinabung.
Good morning, evening, night. Here's more info on Mt. Sinabung. There are more links at the bottom of the story. If you go to the front page of the post, there's a dawn/dusk pic of the eruption that looks pretty impressive.
Video of Mt. Sinabung
#52 @Carl on Iceland:
It's not only the swarms recurrence, but also tremor plots and GPS measurements that show parallel fluctuations, even though kept within standard levels. I can't tell what causes these fluctuations, but just speculate if there could be some sort of common source for them all. Looking forward to hear more from you.
@everyone on Sinabung: Another next VE3 candidate? After 400 years you don't know what to expect. According to linked news there have already been two deaths. Worrisome.
Some news on Sinabung:
For anyone interested in the 1883 Krakatau eruption the fascinating Royal Society report from 1888 is downloadable (PDF 27.2 Mb):
I love this game, this is a great article bring back some memory.
I saw something about this topic on TV last night. Nice post.
Amazing content. Will need a bit of time to think about your points=)
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