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Thread: Let's Talk Iceland

  1. #61
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    Based on all information, my gut feeling is I don't think we are going to see an explosive caldera collapse.

    Activity at the fissure has reduced down to a single vent/cinder cone and the lava flows are slowing down.

    While the Caldera subsidence has reached 23 Meters (75.5 Feet) which is extreme, and has never been seen before in a documented fashion, all appearances say the subsidence is purely based on the magma pool having already been drained into the dyke and fissure.

    I think we will see the fissure activity stop at some point -first-, and then some weeks later, the caldera subsidence will settle down. I will go out on a limb and say the subsidence will probably never reach 50m.

    While the SO2 emissions are still very high, there has not been any emissions from the rim of the Caldera itself, or other signs indicating an explosive eruption potential there yet.

    I honestly think what we are seeing here, is how Caldera subsidence/formation normally works. With the explosive formation of say Crater Lake, being much more rare of a event.

  2. #62
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    Question: I had thought before that Crater Lake, for example, was formed by collapse of a volcano cone into the lava pool beneath, forming the Caldera, subsequent activity of the Caldera such as Yellowstone can heave up and down as lava flows around. Is it the addition of large amounts of water flooding into the lava pool that makes explosion possible, let alone likely?
    sicut vis videre esto
    When we realize that patterns don't exist in the universe, they are a template that we hold to the universe to make sense of it, it all makes a lot more sense.
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  3. #63
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    Quote Originally Posted by dgavin View Post
    Based on all information, my gut feeling is I don't think we are going to see an explosive caldera collapse.
    Most of the larger quakes have been on the caldera's north and southeast sides. Crater floor looks to be behaving like a cork jamming in a bottle sideways. A 6.5 off to the west side could still change that pretty quickly though.
    The one cone that's still active (Baugur) is now is over 200 feet tall. That'll change the character of what we see on cam without necessarily meaning less lava is flowing.

  4. #64
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    Phil Plait has a post up about a "Volconado" at Bardarbunga. Wait 'til the Discovery Channel gets ahold of that! SharkoVulcoNado, or something.
    Cum catapultae proscriptae erunt tum soli proscript catapultas habebunt.

  5. #65
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    Is it the addition of large amounts of water flooding into the lava pool that makes explosion possible, let alone likely?

    Although magma's can change by it encountering water as it pushes to the surface. Basically there are three types. Gas content drives the potential for explosive eruptions.


    Summary Table
    Magma Type
    Solidified Rock
    Chemical Composition
    Temperature
    Viscosity
    Gas Content
    Basaltic
    Basalt
    45-55 SiO2 %, high in Fe, Mg, Ca, low in K, Na
    1000 - 1200 oC
    Low
    Low
    Andesitic
    Andesite
    55-65 SiO2 %, intermediate in Fe, Mg, Ca, Na, K
    800 - 1000 oC
    Intermediate
    Intermediate
    Rhyolitic
    Rhyolite
    65-75 SiO2 %, low in Fe, Mg, Ca, high in K, Na.
    650 - 800 oC
    High
    High
    Source:http://www.tulane.edu/~sanelson/Natu...lcan&magma.htm

  6. #66
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  7. #67
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    Rate of subsidence of Caldera in last 24 hours, 50cm (1/5 meter). Two > 5.0 quakes. While the fissure seems to have stabilized into a single cone, the caldera subsidence doesn't seem to be deceasing, but still on the increase.

  8. #68
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    The seismic activity below the big caldera picked up again today. We had 2 magnitude 5+ quakes in the last 24 hours and several more 3 and 4 mags.

    Something's going on down there. In my layman's mind, I picture high pressure magma melting the mountain of rock and ice that sits atop of Bardarbunga from below. As the caldera sinks in (I think it's gone down by almost 20 meters in altitude since this event started), its tremendous weight keeps acting as an effective plug on the magma pressure below.

    But something below keeps causing the quakes and slippage so I picture it slowly melting the rock above and sending small upwellings of magma through the cracks at the weakest points in the mountain. As it does so, fault-lines are created, the earth slips in, and a big quake is generated.

    So I see the question as, will the pressure from within the Earth somehow dissipate before the plug that is the glacier is breached, or will we see a small eruption, followed by accelerated melting and ultimately a climactic "big one" as the caldera collapses into a magma pool below it?

    And how long is it possible all this could take?
    Last edited by CaptainToonces; 2014-Sep-17 at 06:26 AM.

  9. #69
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    Quote Originally Posted by CaptainToonces View Post
    The seismic activity below the big caldera picked up again today. We had 2 magnitude 5+ quakes in the last 24 hours and several more 3 and 4 mags.

    Something's going on down there.
    You are right, it appears the now 50cm per day subsidence is corresponding to GPS measurements (released today) indicating that the magma flow either out of or into the Caldara (uncertain as to which one) has been changing.

  10. #70
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    Or perhaps the magma is just there, whether flowing in or out, and the cold rock and ice at the bottom of the mountain/glacier is being melted away into the magma.

    At high enough temperature, the rock and ice will lose its crystalline structure and become more like a liquid. That would explain the sinking of the great ice and rock cathedral that is Bardarbunga. Its foundation is melting.

    It would be interesting to see infrared pictures of the area, to measure the change in heat... and even better if we could measure the change in heat about a kilometer beneath the surface. I don't know if that's data that can be obtained though.

  11. #71
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    Stats so far: 0.4 to 0.6 cubic km of lava has been erupted, spanning 37 square km.

    Lava flow has split into two flows, going around the area of the already extruded flow.

    Caldera Subsidence continues a rate from .25m to .5m per day, total subsidence about 27.5 m (Projected from Sep. 14th last published measurement)

    5.5 mag Caldera quake on the 21st.

  12. #72
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    Today's APOD (23/9/14) shows how much light the eruption is putting out.
    That's NOT a sunset!
    http://apod.nasa.gov/apod/

    John

  13. #73
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    The large quakes under the caldera have been definitively linked to subsidence of the caldera's altitude.

    Still though, at 500 centimeters of sinking per day, and these quakes averaging about 5 km of depth (is that correct?), that's still several years until caldera top meets magma...

  14. #74
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    Well the deepest known Caldera is Crater Lake at 593m (1900+ feet) and that was from a catastrophic collapse. So I expect that this one will not subside much given the current gentle trend of it. I'll stand by my 50m max subsidence estimate for now, though it is getting closer to that mark.

  15. #75
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    Quote Originally Posted by JohnD View Post
    Today's APOD (23/9/14) shows how much light the eruption is putting out.
    That's NOT a sunset!
    http://apod.nasa.gov/apod/

    John
    Wow. New desktop for the home computer.
    At night the stars put on a show for free (Carole King)

    All moderation in purple - The rules

  16. #76
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    Updated stats. Lava flow from central cone continues, and still split off into two fields on each side of prior flows.

    Avg. Daily Caldera Subsidence .45m (7m over 15.5 day as a base line) has continued. Last total GPS Subsidence measurement of 24.5m on Sept 17th. Projected out to current day, 30m (96ft) Subsidence.

  17. #77
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    Anybody got a read on if the quakes under Bardar are getting any shallower?

  18. #78
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    They don't seem to be getting shallower, the quakes seems to be stable around the 4-10km range, with an occasional one above that.

  19. #79
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    Looks like a lull tonight.
    Not many earthquakes: two of magnitude 1 in last 5 hours (around 00 thursday).
    Not much activity at fissure either since darkness fell.

  20. #80
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    Quote Originally Posted by CaptainToonces View Post
    Anybody got a read on if the quakes under Bardar are getting any shallower?
    Gallant Capt. T!

    It's BarTHar! BarTHarbunga!!!
    JOhn

  21. #81
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    New cluster of quakes up on the north coast of the island today (Oct 2):
    Seismic activity has been prevalent in Öxarfjörður (Axarfjörður) bay off the northern coast of Iceland, about 5-10 km southwest of the village Kópasker. The largest was 3.3 at 09:03 this morning.
    Map of Mid-Atlantic ridge through Iceland.
    Quake map.

  22. #82
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    Quote Originally Posted by JohnD View Post
    Gallant Capt. T!

    It's BarTHar! BarTHarbunga!!!
    JOhn
    Hmm, maybe they should translate it that way then! I'll refer to it as Bartharboonka from now on.

  23. #83
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    Icelandic uses the "thorn", a crossed 'd' for that soft 'th' sound, that English doesn't bother to discriminate from thr hard version.
    "the, their, them" soft; "thing, think, cloth" hard.

    Here's a helpful Icelander!

    http://www.youtube.com/watch?v=o5t96V-8_TM

    JOhn
    Last edited by JohnD; 2014-Oct-04 at 09:18 AM.

  24. #84
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    Subsidence continues at the .45m/day rate, projected out to 35.4m total so far. While the quake activity at the fissure area has slowed, the lava flow hasn't. SO2 emissions reached Iceland's capital yesterday.

  25. #85
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    National Geographic on-line article about erruption

    A tremendous gush of lava in Iceland that began six weeks ago shows no signs of slowing. The eruption, on a plain of old lava called Holuhraun in the Bárðarbunga volcanic system, has spewed out enough molten rock so far to fill 740 Empire State buildings and has buried, on average, an area the size of an NFL football field every 5.5 minutes.

    At this rate, the lava flow will soon be larger than any seen for more than two centuries in the volcanically active island nation. And there's no telling when it will stop—months, maybe, or years.

    "It's amazing that it has gone on at this rate for so long," says volcanologist John Stevenson of the University of Edinburgh.
    At night the stars put on a show for free (Carole King)

    All moderation in purple - The rules

  26. #86
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    I am thinking that I am going to have to eat my words soon, that it wouldn't reach 50m subsidence...

  27. #87
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    Last few days there looks to be a swarm of earthquakes at Tungnafellsjökull. It's that small glacier/volcano just northwest of Bárðarbunga caldera. Back in late 2013. a swarm there was put down as likely due to increased magma flow into the volcano. With the current eruption steady, and the dike so quiet, I wonder if we might soon be seeing a little eruptive activity from this new location.

  28. #88
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    Tungnafellsjökull has settled down. However in last 48h there've been 73 quakes of magnitude 3+ all around the caldera rim.
    Last week the number was more like 20-30, so there's a definite uptick.
    subsidence of the caldera continues with similar rate as it has done over the last few weeks

  29. #89
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    Total Subsidence projected to 42meters now. Only 8m from my "It won't get to 50m" statement.

    I better start looking for some crows to fix for supper....

  30. #90
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    42 meters, wow. From what i understand, the rock that is this "plug" of a caldera atop Bartharboonga is vast, like an immense amount of Earth. So the energy displacement for that small island to fall 42 meters is quite off the charts.

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