Even the SI/USGS Weekly Volcano Report seems a little light -- welcome to the dog days of summer!
Highlights from this week's report include:
- "Thunderous sounds", incandescence and small plumes (hundreds of meters) with more frequent seismicity at Ibu in Indonesia.
- A sharp increase in sulfur dioxide output was noted at Mayon in the Philippines on August 4 - from ~700-900 tonnes/day to almost 2,000 tonnes/day.
- ~3,000 meter/10,000 foot gas-and-ash plume from Bagana in Papua New Guinea - you can see it on this recent NASA Earth Observatory image.
- Ash/gas plumes from Sakurajima in Japan rose to ~2-4 km / 6,000-13,000 feet and were accompanied by explosions.
- Shiveluch in Kamchatka continues to produce 4-8 km / 13,000-25,000 foot ash plumes related to the dome emplacement/collapse that has been ongoing for the summer. The thermal anomaly at the summit continues to grow, indicating that new lava is causes the dome to grow significantly.
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Speaking of keeping track of volcanoes, here is news about more money for volcano observing.
$2.4 million for the Cascades Volcano Observatory
"In addition to the funding for the Cascades Volcano Observatory, there is also $7.56 million for the Alaska Volcano Observatory, $3.3 million for the Hawaiian Volcano Observatory, $950,000 for Yellowstone Volcano Observatory, $800,000 for upgrading networks in the Commonwealth of the Northern Marianas, and $200,000 for the Long Valley Observatory in California"
Setting aside the politics about whether or not this should have been part of a "stimulus" party, I am wondering specifically what kind of monitering and what kind of insturments will be purchased with this money?
Edit: I should have said "stimulus plan", not a "stimulus party", though maybe there will be some partying going on at the volcano observatories with this new money coming in.
Woot! The web cam at Shishaldin is working again.
Darn its cloudy...
NASA and the USGS put their heads together and came up with something called a Spider (monitoring unit) to put in a volcano. The multiple units talk to each other allowing the scientists to stay at a safer distance.
They have had these spiders at Mt. St. Helens for awhile now ( http://www.komonews.com/news/local/50807692.html ), definitely a good way to study an active volcano, but I am thinking the stimulus money is supposed to help monitor volcanoes before they erupt. Since there already seismographs at all of our cascade volcanoes, I am wondering if there are other insturments that they do not have that would be helpful. Would any of these newer insturments be able to detect volcanic activity before a seismograph detects earthquakes?
I know that by using an array of seismographs and calculating the deflection and speed of seismic waves that magma chambers and structures deep under the surface can be imaged.
Magnetic readings can also help establish underground structures.
Other glimpses into the underground come from monitoring the energy reflected back to the ground surface from lighting strikes and sun storms.
We can also learn by studying other similar volcanoes in other parts of the world.
On another note: large volcanic eruptions affect world climate.
If a volcano in Kamchatka, Indonesia, Alaska or Iceland belches out 20+ million tons of Sulfur Dioxide (SO2) it will cool the Northern Hemisphere - perhaps diminishing agricultural output.
Technologies such as INSAR are helpful in detecting ground deformation and inflation of ground and volcanoes in regions of the world that we can't regularly monitor.
I've been concerned that it is hard to get up-to-date reports on areas of the world that appear to have deep and growing magma chambers. There is at least one area in the central Andes that appears to have a vast deep source of magma - and earthquakes are frequent in the Central Andes. I am not aware if anyone is tracking earthquake trends in the Central Andes to see if these quakes can correlate with any specific stresses and flexing of magma chambers in the area.
One report suggested that large caldera volcanoes in the Andes release magma due to tectonic forces like twisting and buckling of the crust in the area - as opposed to how Yellowstone which seems to be more straight forward gradual melting.
â...But that's where the similarities with Yellowstone end, says Soler. The magma under Yellowstone is thought to be created by the melting of ancient crust under North America, buoying back up and creating a hot spot. Vilama's magma was probably created by a more complex melting of the crust caused by the South American Plate colliding with and overriding the Nazca Plate to the west. The resulting kneading of the crust â the thickening and thinning, pressurizing and depressurizing â caused large pockets of rock to melt and eventually led to a series of gigantic caldera eruptions.
The trigger for the Vilama mega-eruption, says Soler, was probably the same thing that gave the caldera its football-like shape: The tectonic faults in the roof of the magma chamber which probably formed as a consequence of its own instability and/or from the significant stresses in the crust in that area. The crystal-rich nature of the ignimbrites and minimal signs of pre-eruption gases also point to an external trigger for the vast eruption, says Soler.
Much remains unknown about Vilama Caldera, says Soler, largely because it is a terribly difficult caldera to study. Unlike Yellowstone, which has the Yellowstone River cutting through it and exposing the layers of volcanic rock, called stratigraphy, for easy reading by geologists, Vilama is in one of the driest places on Earth. ...â
I know very little about the Andes, but I guess the term âan external triggerâ refers to tectonic earthquakes causing eruptions in this areas. That probably won't happen in our lifetime - but who knows? With the little that is invested in monitoring the Caldera producing Central Andes - probably nobody knows.
Perhaps Indonesia is even more dangerous - its' wet environment quickly erodes evidence of past volcanic activity.
"I know very little about the Andes, but I guess the term âan external triggerâ refers to tectonic earthquakes causing eruptions in this areas. That probably won't happen in our lifetime - but who knows? With the little that is invested in monitoring the Caldera producing Central Andes - probably nobody knows."
Isnt that the scenario for the current Chaiten eruption?
Thomas: fascinating link, thanks. It seems a reversal of the traditional mechanism for caldera collapse: caldera formation triggering ignimbrite eruption rather than ignimbrite eruption followed by collapse. I'm wondering if the Toba caldera -which occupies a (pre-existing?) tectonic graben- might be re-examined in the light of this?
On an entirely separate point: I wish the article had included a location map. Be nice to know if this caldera complex is anywhere near Cerro Galan (the caldera famously discovered through satellite photos) which is also in the Argentinian Andes
Simon, I think that Chaiten is away from the area that produced massive Caldera eruptions in the past.
The Central Andes area that I am thinking about is the Bolivian, Chilean, Argentinian border area.
This area, Mike, (see the map link in this comment) has a Cerro Galan close to or maybe in a *Reserva Nacional de Fauna Andina Eduardo Abaroa* which I am guessing might correspond with this description in the article I linked to from geosociety. The map doesn't show the outline of the National Reserve so I can't know how close the reserve is to the border of the three countries or Cerro Galan. So if I search âCerro Galanâ at the right of the map page and click it one of the âhitsâ for this phrase appears very close to the Eduardo reserve - maybe it is in - or just outside the Caldera Complex.
The geosociety link that I put up in my last comment points to the article which says Vilama is one of
âseveral unappreciated supervolcanoes hidden in a veritable mega-volcano nursery called the Eduardo Avaroa Caldera Complex, located in the inhospitable Puna-Altiplano region near the tri-section of Argentina, Bolivia, and Chile.â
It seems to fit the description but I can't spot the Cerro Galan caldera by eye off this satellite map though. It does appear to be in the right area.
I've got Google earth - but it often over-taxes my videocard.
Wikimapia dot org still gives me great zoom capability and it has some volcanoes that show up when a mouse is hovered over it.
I didn't know Toba was in a graben.
You can clearly see Laguna Diamante from here.
25Â°58'4"S 67Â°5'11"W use those co-ords for google earth and its gets pretty close.
Mike Don and Simon,
The link provided by Simon does look to be a real volcano for Cerro Galan. The other Cerro Galan near the Eduardo Avaroa Caldera Complex (the one I pointed to) is just one other area with the same name - No wonder I couldn't find the caldera at that location - there was none!
I was just wondering what the latest was on the threat of a Volcanic Eruption near Al-Ais - so I checked into it.
It appears that the evacuees still haven't been allowed to return.
One visitor to Eruptions gave a link to a page where Google translates the Saudi seismic news. From what little I can understand of it - and I don't know the place names they mention - there does continue to be low level seismic activity of two and three on the Richter scale.
At the link above there is paragraph size article titled, âOfficials may end Al-Ais evacuationâ
I remember they were close to ending the evacuation a few months ago - but then there were some more earthquakes - and they decided to wait until the earthquakes ended. The earthquakes never really ended they just got smaller and gradually less frequent. The Saudi Government is paying for Evacuees to stay at hotels and apartments in other areas.
I am guessing, that since the meeting to decide the fate of the evacuees has by now taken place and I didn't see another news story on it - that their is no change in the status of the evacuees. They probably still hope to return them soon to their village - but want to see things calm down a bit more so they don't have issue another evacuation if there be some slightly stronger quakes again.
Simon, looking back over my comments I just wanted to make sure that you realize that I wasn't disputing that Toba was in a graben. As a matter of fact I had to look up the term graben to see what it meant. It is an area between faults where the ground has dropped down a bit. (I've got a lot more to learn about geology - and I think I'll delve more into my five year old geology textbook that I picked up for 25 cents at a church rummage sale.)
So my comment that I didn't know Toba was in a graben - I just meant to say that I learned something.
Here is a good definition, illustration and cited examples, for anyone else who wants to learn more about grabens.
Hadnt even thought about Toba to be honest so no worries. I didnt know it was in a graben either so you have taught me something :)
Simon, ... OOOPS. It was Mike Don that made the initial comment about Toba being in Graben. I ought to have directed my clarification to Mike Don who made the initial statement to me about Toba. I should have reassured him that I wasn't challenging his comment. I am glad that his comment helped me to research what a Graben is and learn more geology.
Here is one website that I found valuable and intend to review some more to learn more geology.
The few sessions that I have watched were informative. I want to watch the rest and review what I've already learned.
Annenburg/CPB (learner dot org) has video classes (including geology based) available, but only US and Canadian residents are permitted to watch them due to licensing agreements.
NPTEL from India has many free courses available to watch online including Engineering Geology. Anyone with a fast internet connection can watch any of their internet video classes (about 4,000 separate class sessions are available.)
I am sure there are other video classes online too ... in more American English.
I've got so much to learn in so many fields ... trying to learn some basic algebra right now ... and many other things God may want me to do.
The Puerto Rico area had about 28 earthquakes greater than 3.0 on the 14th including a 4.7
The USGS website shows earthquakes greater than 2.5 for US territories - but only shows 4.5 quakes and larger for non US areas.
Are there other areas of the world that consistently have as much seismic activity as Puerto Rico - three and four Richter scale quakes that are not showing up on the USGS site that are outside US territory? I need perspective on how to categorize what is happening in Puerto Rico - but the USGS is using different scales for US and non-US territories. Is the rate of quakes near Puerto Rico similar to other areas near deep subduction zones - or is something really out-of-the-ordinary going on in Puerto Rico?
I'll be glad to get any help on this question. It has been bugging me for a while.
The USGS site is brilliant but it doesn't always pick up every quake and often USGS scales quakes lower than local networks so they drop below the 4.5 threshold. As a comparison the NZ geonet earthquake site has reported 10 M3 quakes and 5 M4 quakes in the last ten days (disregarding the aftershocks from the recent M7 quake down in Fiordland). This is a little higher than the average but not much. i.e. there is a lot of activity that doesn't get on to the USGS radar, and that is just New Zealand. Regions that are really active like Tonga would display much higher levels than this. I've also often noticed a quake that Geonet rates M5 not being registered by USGS and we all know there were a lot of similarly sized quakes down at Chaiten that didn't make it on to the USGS site. Why, I don't know.
As for the Graben/caldera thing, it makes perfect sense to me. In a subduction scenario the leading edge of the overriding plate often gets chewed in a bit which stretches the crust behind it, effectively thinning it, in precisely the place where melt from the subducting plate rises to fuel volcanic activity. On top of that the faults in the graben facilitate upward movement of magma, so you get a lot of melt, thin crust and then seismic activity to trigger eruptions, most of which, thankfully, are not caldera forming ones, but every now and again..
Thomas and Simon;
Thanks for all the information. After saying that Toba was a graben (from a vaguely remembered description) I thought I'd better verify my statement. Some googling found this:
So I wasn't dreaming it, whew!
Bruce S. your comment was helpful. It confirms that it is hard to compare apples with apples when it comes to earthquake activity around the world.
Here is the latest on the inflation at the central Andes areas of Lazufre.
I've only been able to read the abstract which I will copy below.
The variable spatio-temporal scales of Earth's surface deformation in potentially hazardous volcanic areas pose a challenge for observation and assessment. Here we used Envisat data acquired in Wide Swath Mode (WSM) and Image Mode (IM) from ascending and descending geometry, respectively, to study time-dependent ground uplift at the Lazufre volcanic system in Chile and Argentina. A least-squares adjustment was performed on 65 IM interferograms that covered the time period of 2003â2008. We obtained a clear trend of uplift reaching 15â16 cm in this 5-year interval. Using a joint inversion of ascending and descending interferograms, we evaluated the geometry and time-dependent progression of a horizontally extended pressurized source beneath the Lazufre volcanic system. Our results hence indicate that an extended magma body at a depth between 10 and 15 km would account for most of the ground uplift. The maximum inflation reached up to ~ 40 cm during 2003â2008. The lateral propagation velocity of the intrusion was estimated to be nearly constant at 5â10 km/yr during the observation time, which has important implications for the physical understanding of magma intrusion processes.
The wording to me has some ambiguity. What does ânearly constantâ mean over a five year period when the range of movement is given âat 5â10 km/yrâ one number is twice that of the other. And I guess lateral propagation means the magma chamber is developing sills (?) or the magma chamber is growing in diameter?
Does anyone else know what this means? A few years back INSAR produced some data showing accelerating inflation at Lazufre. I haven't yet been able to compare the rate determined by INSAR to this rate cited in the abstract. I have yet to be able to reconcile some numbers just from reading the abstract.
âWe obtained a clear trend of uplift reaching 15â16 cm in this 5-year interval.â
âThe maximum inflation reached up to ~ 40 cm during 2003â2008.â
Can anyone access the report and explain the seeming disparity? If the uplift over a five year period is about 15cm per year on some years, then was this an earlier year or a later year? 15cm times five years equals 75cm total not the 40 cm total given. This indicates a change of speed - is going faster or slower as time goes on - while the lateral propagation remains ânearly constant at 5â10 km/yrâ?
If anyone has professional access to this report could you answer these questions?
When I get around to checking on the rate of acceleration in the INSAR report I'll post about what I find.
The Andes are certainly extremely interesting. I am sorry I can't make much of the abstract either, particularly the rate of lateral intrusion of 5-10 km/year which sounds very fast to this layman. Assuming they are talking about a sill as it sounds then that would imply a very high volume of ascending magma.. Then again we know from other calderas like Yellowstone and Taupo that they go up and down like yo-yos so I guess we shouldn't get too excited yet.
Re the Graben thing, I guess I oversimplified it (a common fault of mine).. no doubt there is a whole lot of complex tectonics involved, with folding and faulting going on as well. When you think about it Toba (elev. 900m) and the Andes calderas (also I presume pretty high elevation) must be sitting on a good wad of continental crust too, so the thin continental crust thing only works to a certain degree. It is, however, particularly evident in the Taupo volcanic zone where the Havre Trough is stretching open behind the leading edge of the Kermadec Trench.
There is another abstract that you can look at here regarding Lazufre. It was from two years earlier.
Here is what the abstract says.
Copyright Â© 2008 Elsevier B.V. All rights reserved.
Caldera-scale inflation of the Lazufre volcanic area, South America: Evidence from InSAR
J. RuchCorresponding Author Contact Information, a, E-mail The Corresponding Author, J. Anderssohna, T.R. Waltera and M. Motagha
aGeoForschungsZentrum Potsdam, Telegrafenberg, D-14473, Potsdam, Germany
Received 30 August 2007;
accepted 6 March 2008.
Available online 26 March 2008.
Collapsed calderas are the structural surface expression of the largest volcanic eruptions on Earth and may reach diameters of tens of kilometres while erupting volumes larger than 1000 km3. Remnants of collapse calderas can be found along the South American volcanic arc and are thought to be inactive. However, this study shows that systems of such dimension may become active in a relatively short period of time without attracting much attention. Using satellite-based InSAR data, a 45 km wide elongated area of ground deformation was observed in the Lazufre volcanic region (Chile), where no deformation was detected 10 years ago. The deformation signal shows an uplift of up to ~ 3 cm yrâ 1 during 2003â2006, affecting an area of about 1100 km2, comparable in size to super-volcanoes such as Yellowstone or Long Valley. This deformation signal can be explained by an inflating magma body at about 10 km depth, expanding and propagating laterally at a velocity of up to 4 km per year. Although it is not clear whether this intrusion will lead to an eruption, its dimensions and the rapid deformation rate insinuate that a potentially large volcanic system is forming.
2. The 2003â2006 deformation
2.1. InSAR data
2.2. Volume and area increase
2.3. Source modelling
3.1. Limitations of the models
3.2. Multiple source evidence
3.3. The comparison to other inflation caldera systems
3.4. Source origin
3.5. Earthquake triggering of magma intrusion
3.6. Total volume of the source
Fig. 1. Shaded relief map of the central Chile volcanic arc and the location of the inflation at the Lazufre volcanic area. Older caldera systems are shaded in light blue, with faults are marked by black lines.
This older study suggests the earlier magma intrusions were less pronounced than the more recent time frame that concluded in 2008 (two-years later).
The analysis of the satellite reports are published sporadically and don't deal with up to the minute data. We should probably monitor seismic activity in the area to see if there are any seismic indications of incipient volcanic unrest.
In an 11 July 2002 letter to Nature titled,
A satellite geodetic survey of largescale
deformation of volcanic centres
in the central Andes
Matthew E. Pritchard & Mark Simons
Seismological Laboratory, Division of Geological and Planetary Sciences,
California Institute of Technology, Pasadena, California 91125, USA
it was written in the 2002 letter,
âLazufre and Robledo also lie near regions with low seismic velocities.
The deformation source near Hualca Hualca could be
related to activity at Sabancaya, even though it is 7 km away. During
the 1990 eruptions of Sabancaya, a concentration of earthquakes
was located between 4â7 km depth in about the same region as our
inferred deformation source. A large distance between an eruptive
centre and the magma chamber has been inferred elsewhere; for
example, in Alaska, where the 1912 Novarupta eruption was at least
partially fed by a magma chamber beneath Mt Katmai 10 km
distant. Lazufre also lies more than 7 km from the nearest
potentially active volcano. This inferred deformation source could
plausibly feed either of the nearby volcanoes, orâas it lies within a
topographic depressionâit could represent an incipient caldera.â
Oh well, we can keep an eye on it anyway.
Bruce; re Toba & Graben
I would have thought that overlying area would be under considerable compression due to the nearby subduction zone .. if a graben exists there i would have put my money on some shear component to the subduction shearing Sumatra apart somewhat (along an appropriate fault, as opposed to "chewing up" & thinning , but maybe we are saying the same things , but in different ways .. what do you think ??
Just to chime in quickly, grabens along volcanic arcs are relatively common. There are grabens in the central Oregon Cascades and along the Altiplano-Puna in the central Andes. Most of these are caused by crustal thickening leading to isostatic compensation for the overthickening by rifting (at least in the high Andes). Whether the rifting accommodates more/less magmatism is unclear, but it isn't too uncommon to find it in arc settings.
Robert, I am glad Erik has put it in language that makes more sense!!
The chewing thing I need to explain though, as what I had in mind was the East Cape of New Zealand where there is indeed shear going on, and, although it is situated on the over-riding Australian plate, it is getting slowly ripped away from the rest of the Australian plate and dragged into the Kermadec trench (well at least it is if I have understand the material on the Geonet site properly) and this is what is opening up the graben where the Taupo volcanic zone is situated, although I must admit it does sound a bit counter-intuitive to me in retrospect. I have heard it explained as frictional drag caused by the subducting plate taking some of the overriding plate down with it.
This also sounds to me like a different mechanism to isostatic compensation which I understand (please correct me if I am wrong) as downwards buckling or even rifting of the overriding plate behind a range of mountains getting forced up by compression on a plate boundary), an example being the Marlborough Sounds in NZ that are slowly sinking, or the Tyrrehnian (sp?) Sea in the Med.
(PS sorry for the all the kiwi examples, it just happens to be the place I know best!)
Eric & Bruce;
I am having problems visualizing how an area close to a subduction zone (presumably under considerable regional stress due to subductive forces) could under go rifting .. I can visualize differential faulting (maybe even a pseudo-graben) due to rebound of thickening crust ... I need a diagram to break out of this logical conundrum (isn't the first time i have faced this confusing geologic issue ..) Can you help ?