iceland Bárðarbunga and Askja - Volcanic Activity

[john pike]

http://vmkerfi.vedur.is/vatn/vdv_data.php?Type=VV&Station=Austurland%40%40222&First=2014-09-29+01%3A00&Last=2014-10-01+01%3A00&Pageid=342&PageName=J%F6kuls%E1+%E1+Fj%F6llum%2C+Gr%EDmssta%F0ir%3B+V102&PageType=Graph&Nrofgraphs=1&Graphnr=1&Plot&lower=0&upper=50&X=0&language_id=4&screen_width=1688&screen_height=860&request_type=2&qc_view=0&borun=0#

[The PIT]

Going well this morning little in the way of quakes I guess due to wind once more.

[swebby]

It may be a trick of light or wind direction on the plume but the main cone looks as if it has grown significantly in height from yesterday.

 

GPS also looking as if the caldera may be undergoing another slump.

[karyo]

It could be that the wind is a bit lighter allowing the plume to rise.

[Tom Jarvis]

Large quake incoming poss 5+m

[john pike]

Tuesday
30.09.2014 14:53:19 64.679 -17.469 6.6 km 4.7 99.0 5.1 km NNE of Bárðarbunga Tuesday
30.09.2014 14:51:00 64.058 -21.195 5.3 km 1.3 99.0 2.2 km S of Hrómundartindi Tuesday
30.09.2014 14:34:31 64.683 -17.661 6.1 km 1.6 99.0 7.9 km NW of Bárðarbunga Tuesday
30.09.2014 14:31:12 64.815 -16.896 6.5 km 0.9 99.0 15.2 km ENE of Kistufell Tuesday
30.09.2014 14:13:36 64.667 -17.492 3.6 km 3.8 99.0

3.4 km NNE of Bárðarbunga

 

Tuesday
30.09.2014 14:03:17 64.671 -17.436 1.0 km 2.9 99.0 5.5 km NE of Bárðarbunga

http://en.vedur.is/earthquakes-and-volcanism/earthquakes/#view=table

 

Edited September 30, 2014 by john pike

[john pike]

http://www.livefromiceland.is/webcams/bardarbunga/

 

looks like the viewing of the cam is about to be lost again

[john pike]

twenty Five Thousand Earthquakes By Benedikt Jóhannesson September 30, 2014 06:49 Updated: September 30, 2014 08:21

The eruption is setting records every day. Photo: Jóhannes Benediktsson

Around 25,000 earthquakes have registered on Icelandic Met Office’s equipment since August 29. The eruption is one of the largest in the world. All in all 39 quakes over 5.0 have been recorded, most of them in the rim of the Bárðarbunga crater. The eruption itself is to the north of the sub-glacial volcano which makes a lot of difference, because that means the ash and flood danger is limited.

On Monday a quake of magnitude 5.5 occurred, the second biggest from to beginning of the eruption.

Volcanologist Ãrmann Höskuldsson says that the eruption is not only big but interesting in other respects as well: “The flow of magma to the surface is extensive and the lava fountains are going high up in the air. The flow of poisonous gas is also unusually high. We have to go back to the Lakagígar eruption to find anything similarâ€.

Ãrmann says he has no idea how long the eruption will last. „It has already lasted longer than I anticipated“.

 

http://icelandreview.com/news/2014/09/30/twenty-five-thousand-earthquakes

[swebby]

IMO now have it listed as M4.7.

 

I've been following the GPS plot of the caldera and I am still trying to work out if the apparent short term increases in altitude (the bumps against the downward trend in the blue line that have periods 2-4hrs) are real or artifacts?

 

They seem to occur regardless of weather, temp or time of day and are to short/random to be tidal so I guess they could be real. 

 

I have in my head two ideas. 

 

One - of pressure building against the caldera roof causing uplift and then releasing but I would assume this would be accompanied by an identifiable EQ pattern?

 

Two - Every time the caldera floor slumps, the ice sheet moves (flows) towards the centre of the slump and kind of rebounds (sloshes) but I would have thought this would take longer than 2-4hrs?

[BrickFielder]

  Lots of noise on ther tremor charts from the weather over the last day so I am looking at those charts with a sceptical eye. There is also a bit of dicussion on blogs about the Bárðarbunga GPS measurements and whether there really is some sort of bouncing around on short time scales.

 

Source for this picture is the Icelandic Met Office Site.

 

Note :

 

Disclaimer: These graphs are for civil protection use and to inform the public. They are not to be used in scientific publications without permission.

 

http://en.vedur.is/earthquakes-and-volcanism/gps-measurements/bardarbunga/caldera

 

 

Haraldur Sigurðsson's blog seems to be the source of the conversation with a suggestion that perhaps there is ice melt contributing to the caldera subsidence and perhaps the small bouces are a result of this.

 

Source  (although you might need to translate it.

 

http://vulkan.blog.is/blog/vulkan/entry/1452885/

 

 

I think the GPS plots need another look at in terms of what they suggest.

 

 

This seems to be the GPS device nearest the eruption and I would interpret this as showing a rifting event which is begining to wane in its intensity. That is not to say the eruption will stop, but rather the fissure near to the GPS device does not appear to be opening up more.

 

 

This is south west of the caldera and would suggest to me movement during the rifting period and then some uplift towards Bárðarbunga.

 

 

This is north west of the caldera and would suggest to me movement during the rifting period and then some uplift towards Bárðarbunga.

 

Lets try to visualize this on a map of the SIL positions.

 

 

Source of charts is the university of Iceland Web site

 

http://jardvis.hi.is/gps_timaradir_vid_bardarbungu

 

 

This might suggest some sort of uplift towards the western/ south western edge of Bárðarbunga's caldera.

 

Taking a closer look though and both the HAFS and VON GPS dont show significant up down movement, so any uplift must be very near to Bárðarbunga.  Yet we know that Bárðarbunga caldera is subsiding.  I dont buy into the fact that subsidence in the caldera is solely about ice melt. Surely any melt water would be seeping down to cause problems deeper down or going somewhere ?

 

We have however seen some earthquakes which look suspiciously like ice quakes.

 

Monday 29.09.2014 15:10:12 Depth 0.0 km     Magnitude 2.5    5.1 km ESE of Bárðarbunga.

 

Zero depth but very big for an icequake. Seems more like a crack opening up in the caldera floor due to all the bouncing around to me.

 

Whats with having very few earthquakes in the south west corner of the caldera. Ok so we suspect that the ring faults are different at different points around the caldera.

 

From one of my previous posts.
 

Our results favour outward-dipping fault segments in the western half of the ring fault, while the eastern half is preferentially inward-dipping. This variability may reflect structural heterogeneities or an irregular magma chamber geometry. The individual segments of the caldera ring fault radiated approximately equal amounts of energy. This indicates that the caldera dropped coherently as one single block.

 

 

This kind of makes me think about trap door collapses of calderas and the 1968 collapse event in Fernandina (Galapagos) . Even that does not feel right.

 

Perhaps there are multiple magma chambers like Grímsvötn with one feeding the north fissure and one the south fissure. Again I am not convinced  since it does seem to be slipping as a single block. The difference in the ring faults might explain parts of it, but there might be another reason.

 

Yes here I go into back into the whacky world of theory. We suspect that during the krafla fires eruption to the north of Bárðarbunga that fissures north and south of there may have come under compression as the fissure opened up, only to relax some considerable time after the eruption.

 

Kind of like.

 

 

So you could have compression pushing up the caldera to the south while magma flow and expansion let the caldera drop to the north. The problem is I dont quite see the transition from compression to expansion occuring across the relatively small scale of Bárðarbunga's caldera.

 

Yet another theory with more holes in it.

 

Have you noticed that most of the big earthquakes that cause subsidence in the caldera seem to occur between 5 and 8km deep and often close to 7km deep while other earthquakes even if quite large dont seem to affect the caldera. Certainly seems worth thinking about as to what exactly is happening at that depth  (we have a suspicion that the magma chamber is down at around 10km).

 

29.09.2014 13:42:58 Depth 5.6 km Magnitude 5.5 8.5 km ESE of Bárðarbunga

 

There is also discussion on blogs about whether the eruption is being fed from Bárðarbunga's magma chamber.

 

Ãrmann Höskuldsson, commenting on the occasion of the 1 month anniversary of the eruption points out that not only are there extremely deep quakes under Bárðarbunga, but also under Dyngjujökull and Holuhraun, suggesting that "it's not all coming straight from Bárðarbunga, but rather from deeper."

http://www.mbl.is/frettir/innlent/2014/09/29/otrulega_mikill_kraftur_i_gosinu/

 

 

Personally I think this is half right, in that the magma source is essentially the same for the eruption and Bárðarbunga's magma chamber but the flow is not direct from the magma chamber any more, but from the deeper source.

 

Back at the eruption and there are suggestions that the northern flow of lava which crossed and wiped out the road in the area may have come to a stand still, while flows to the south towards the river have picked up. I think it will be interesting to see how far it gets over the next  day or so and its impact on the river.

 

As ever there is a caveat emptor on anything I write, in that these are very amateur observations and I dont expect anyone to buy into what I am thinking. Still it is fascinating and perplexing.

Edited September 30, 2014 by BrickFielder

[john pike]

 

 

another jolt again

 

Edited September 30, 2014 by john pike

[swebby]

Good post as always BF.

 

Blue line on GPs - suggesting someone has picked it up and run off with it?  Think i'll put this one down to weather.

 

Tremor charts also subject to weather variations over the past few days but a number are certainly showing an upward trend in base line over the past 2 week period.

[john pike]

http://www.nat.is/travelguideeng/geology_plate_tectonics.htm

 

http://platetectonics.com/oceanfloors/iceland.asp

 

An important effect of the melting of subducted ocean crust is the production of new magma. When subducted ocean crust melts, the magma that forms rises upwards from the plane of subduction, deep within the mantle, to erupt on the earth's surface. Eruption of magma melted by subduction has created long, arc-shaped chains of volcanic islands, such as Japan, the Philippines, and the Aleutians. Where an oceanic tectonic plate is subducted beneath continental crust, the magma produced by subductive melting erupts from volcanoes situated among long, linear mountain chains, such as the Cordillera, up to 100 km inland from the zone of subduction. (The zone itself is located along a submarine trench offshore of the continent.) In addition to creating and feeding continental volcanoes, melting of subducted ocean crust is responsible for the formation of certain kinds of ore deposits of valuable metallic minerals.

Integrated Plate-Tectonics Theory.  With this knowledge of seafloor spreading and subduction zones, all that remained was for the ideas to be combined into an integrated system of geodynamics. In the 1950s, the Canadian geophysicist J. Tuzo Wilson demonstrated the global continuity of the subduction zones, rather like the stitching on a football. The American geologist Harry Hammond Hess argued that if the ocean floor were rifted apart in one part of the globe, the expansion that would result there had to be accommodated by subduction in another part; otherwise the earth would grow larger and larger. Xavier LePichon, a French student of seismology at Lamont, worked out the geometry of the plates from seismic evidence, and the American geophysicist Robert Sinclair Dietz took Wegener's evidence of continental drift and reconstructed the positions of the continents and oceanic plates in successive stages back in time to about 200 million years ago. Since then, the theory of plate tectonics has been debated, tested, and expanded and has become both a paradigm and a centre of controversy for the geological sciences.

 

the part that has interested me in this is the point

 

The American geologist Harry Hammond Hess argued that if the ocean floor were rifted apart in one part of the globe, the expansion that would result there had to be accommodated by subduction in another part; otherwise the earth would grow larger and larger

 

now the thing i have noticed is the reduction of larger quakes anywhere since this event started

 

http://earthquake.usgs.gov/earthquakes/eqinthenews/

 

maybe 2 since this started

 

so if the above by harry hammond is correct this could keep going until activity starts off again elsewhere

 

so i am waiting to see if a big quake happens and this slows down or stops

 

http://www.dailymail.co.uk/sciencetech/article-1385589/The-growing-gap-Eurasia-North-American-tectonic-plates.html

 

have a look at the link above

 

not my ideal source but good pics there

 

nice post bf

 

i have my ideas but have decided to watch now as i think its baffling everyone at present

 

 

http://www.livescience.com/31566-iceland-tectonic-plates-meet.html

 

another interesting read

Edited September 30, 2014 by john pike

[john pike]

Tuesday

30.09.2014 15:48:03 64.671 -17.468 2.9 km 3.0 99.0 4.4 km NE of Bárðarbunga Tuesday

30.09.2014 17:51:50 64.676 -17.469 3.0 km 2.4 99.0 4.8 km NE of Bárðarbunga

http://en.vedur.is/earthquakes-and-volcanism/earthquakes/vatnajokull/#view=table

[Allseasons-Si]

Evening all

 

this is nice viewing from a member of the chat room on youtude

 

 

nice post btw BF

 

also a lovely evening on mila cam 1 again,stunning,with the steam visable from where the lava meets the river,and a wintry anvil in the backdrop.

 

http://www.livefromiceland.is/webcams/bardarbunga

Edited September 30, 2014 by Allseasons-si

[john pike]

30th September 2014 18:50 - from geoscientist on duty

Since midnight, just over 40 earthquakes have been located at Bárðarbunga and just over 30 in the intrusive dike. Especially in the dike, these are somewhat higher numbers than at the same time yesterday which could stem from the fact that it has been less windy today (as explained yesterday, high winds can blur the detection of small earthquakes). No earthquake has reached 5 in size today; yet three quakes were over M4, all in the northern caldera rim of Bárðarbunga, at 14:53 M4.7 and at 03:06 M4.0 and at 07:57 M4.2. The largest earthquake in the dike was just after midnight, M2.4. According to web cameras, the eruptive activity is of similar intensity as recently.

 

http://en.vedur.is/earthquakes-and-volcanism/articles/nr/2947

[Allseasons-Si]

Gps dropping like a stone,a biggy comming perhaps!,4.5 maybe bigger!

 

http://hraun.vedur.is/ja/Bardarb/BARC/

Edited September 30, 2014 by Allseasons-si

[john pike]

hi allseasons

 

your probably right

 

this has just jumped

 

also looking at mila 1 i am wondering whether we are seeing a new fissure opening

and on q

 

theres the quake

[NorthNorfolkWeather]

hi allseasons

 

your probably right

 

this has just jumped

 

also looking at mila 1 i am wondering whether we are seeing a new fissure opening

and on q

 

theres the quake

Big quake that

 

For the new fissure John did you mean the activity on the left of the shot?

[john pike]

hi north

 

yep the left of the shot

 

but as allseason has pointed out it may be a water reaction and lava mix

 

lets see if it gets bigger, it certainly looks interesting

[Allseasons-Si]

As we know water and fire doesn't mix,boom!!!

 

it sure looks v interesting though guys,we will find out sooner or later

 

Edit:4.8 ver'd @8.4km

 

http://baering.github.io/

 

make of what you see,i still don't know!

 

http://www.livefromiceland.is/webcams/bardarbunga-2/

 

Edit 2:yeah,look at the line of lava there,defo lava meeting the river

Edited September 30, 2014 by Allseasons-si

[john pike]

hi allseasons

 

http://en.vedur.is/earthquakes-and-volcanism/earthquakes/#view=table

 

south east this time

 

http://www.emsc-csem.org/Earthquake/seismologist.php

 

a word of caution for anyone that reads these

 

you do get rogue quakes sometimes

 

and a 5,3 in the uk i reckon would get noticed

[Allseasons-Si]

hi allseasons

 

http://en.vedur.is/earthquakes-and-volcanism/earthquakes/#view=table

 

south east this time

 

http://www.emsc-csem.org/Earthquake/seismologist.php

 

a word of caution for anyone that reads these

 

you do get rogue quakes sometimes

 

and a 5,3 in the uk i reckon would get noticed

EH!!!,just looked at that,i have just had a rash of goosepimples rush over me lol!

 

that cannot be right can it!!!

 

big drop on the gps with that EQ.

[If Wishes made Weather]

GPS now falling away very rapidly:

 

[john pike]

hi allseasons

 

no im pretty sure its wrong

 

faulty instruments i assume