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Posts Tagged ‘Asolfsskali var’

Eyjafjallajökull Erupting – UPDATE: 20 Apr

Posted by feww on April 20, 2010

Considerable volcanic activity is occurring at three separate craters at Eyjafjallajökull, with explosions heard continually

Plume of ash is reaching a height of about 6,000m asl. The ash is accumulating around the edge of the craters and is beginning to form a rim. Lava splatters were earlier ejected to a height of about 3 km this morning.

The visibility in the vicinity of Eyjafjoll and at Asolfsskali var was reported at 500 meters, about two hours ago (~ 07:00UTC).

“There is no risk of flash floods because the water is continuously flowing off the glacier.” Local experts said.

Iceland Met Office  (IMO) – Update on activity
Eruption in Eyjafjallajökull, Iceland
Sound blasts – 20 April 2010 at 12:30(UTC)

Heavy sound blasts have been heard and found near Eyjafjallajökull, especially south and east of the mountain, and more clearly after wind speeds became lower. Possible explanation: Very hot gases rise from the eruptive channel. When surfaced, the temperature of the gases drops sharply with abrupt changes in pressure. These result in shock- and sound waves which can be carried long distances in air. END.

Volcanic Ash Drift from Iceland’s Eyjafjallajökull Eruption

This image uses infrared data from the Meteosat Second Generation (MSG) satellite to generate a false colour composite image. This presents information about the infrared radiation being emitted by the ash plume, and by surrounding clouds, at several different wavelengths. Because cloud particles and volcanic ash particles interact with the infrared radiation in different ways, they show up as different colours when the data are presented in this way (but it is important to note that these are false colour images, and the colours do not correspond to the actual colours that would be seen by the human eye). Please refer to the forecaster blog to read the latest information regarding the evolution of the plume. Caption: UK Met Office

How Bad is the Ash Drift in the UK?

A spokesman for UK’s National Air Traffic Service (NATS) said: “The volcano eruption in Iceland has strengthened and a new ash cloud is spreading south and east towards the UK. This demonstrates the dynamic and rapidly changing conditions in which we are working.  Latest information from the Met Office shows that the situation is worsening in some areas.”

Latest Eruption Images from the Webcams – Click images to enlarge

Eyjafjallajökull seen from Hvolsvelli

Eyjafjallajökull seen from Thórólfsfelli

Eyjafjallajökull seen from Valahnúk

Image of Ash from Eyjafjallajökull by NASA’s MODIS

Large plume of ash and fumes is seen spewing out of the volcano’s craters.

Eyjafjallajökull Captured by ALI on NASA’s EO-1 satellite

Download large image (2 MB, JPEG)

Ash Drift Graphics Issued by Volcanic Ash Advisory London, UK

Animation of an Advisory Chart

This is an illustration of volcanic ash dispersion up to 20,000 ft, issued at 7 am (06:00UTC) on 20 April. Advisory charts are issued every six hours, for up to 18 hours ahead, by the Volcanic Ash Advisory Center, London, UK.

Polar Orbiter Imagery

These images show the progression of the main volcanic ash plume from Eyjafjallajökull on April 15, as detected using data from polar orbiting satellites operated by NOAA and EUMETSAT. As with the MSG images, these make use of the varying properties of the ash particles at different wavelengths. The ash cloud signal is yellow and orange in this sequence. The early images are able to detect only a very narrow section of plume close to the Icelandic coast, mainly because of the presence of higher-level ice clouds which are obscuring much of the ash below. Succeeding images show the ash plume developing more clearly as it spreads eastwards. Caption: UK Met Office.

Cross-Sectional Diagrammatic Representation of What Eyjafjallajökull and Katla might look like

For more information email Páll Einarsson (palli@raunvis.hi.is)

Insight into the eruption of Eyjafjallajökull from GPS data – Sigrún Hreinsdóttir and Þóra Árnadóttir [Source: Institute of Earth Sciences- NVC]

20. April 2010: Latest results from GPS stations around Eyjafjallajökull show deflation associated with the eruption. No movements associated with the Katla volcano are presently observed – Benedikt Ófeigsson and Bryndís Brandsdóttir

In the first two days of the Eyjafjallajokull volcano summit eruption (14. April), two GPS stations located north (STE2) and south (THEY) of the summit crater moved rapidly toward the eruption site (about 6 cm contraction between stations). Modeling of the GPS data suggest deformation due to a volume change of a shallow magma source (1 km depth). This is consistent with chemical analysis of the magma erupted, intermediate chemical composition (58 wt% silica) (Níels Óskarsson). The volume decrease estimated from the GPS data (3-10 million cupic m) is however only a small portion of the volume estimated to have erupted in the first few days (Magnús Tumi Guðmundsson et al.). GPS stations around Eyjafjallajokull volcano (http://notendur.hi.is/runa/eyja_gps.html) show continued deflation of the region, but now at a much slower rate at the stations closest to the summit. This could indicate continued deflation of another and deeper magma source.

Volume of erupted material and magma discharge for the first 72 hours

The Institute of Earth Sciences has now made a preliminary estimate of erupted material in the first three days of the eruption at Eyjafjallajökull. The erupted products are fragmented material, the majority fine-grained airborne tephra. Eruptive products can be split into three categories:
1. Material (tephra) in the ice cauldrons around the volcanic vents.
2. Tephra filling the glacial lagoon of Gígjökulslón, carried by floods down the outlet glacier Gígjökull.
3. Airborne tephra that has been carried to the east and south of the volcano (see memo by Thorvaldur Thordarson, Guðrún Larsen and Ármann Höskuldsson, pdf-file)

The preliminary results are as follows:
Tephra in ice cauldrons 30 Million m³
Tephra in Gígjökull lagoon 10 Million m³
Tephra fallout from eruption plume 100 Million m³
Total: 140 Million m³

The tephra is uncompacted, these values corresponds to some 70-80 Million m³ of magma. The average magma discharge rate is about 300 m³/s or 750 tonnes/s.
This is 10-20 times the averge discharge rate in the preceeding flank eruption at Fimmvörðuháls.

Magnús Tumi Guðmundsson; Þorvaldur Þórðarson; Guðrún Larsen; Ármann Höskuldsson; Þórdís Högnadóttir; Eyjólfur Magnússon
[Source: Institute of Earth Sciences- NVC]

How fine is the ash?

After the ashfall in the 14-16 April eruption, the Environment Agency collected samples  from Mýrdalssandur (50 km away from the eruption site), which were then  analyzed by Institute of Earth Sciences . The ash had a high fluorine content and was fine grained in the follows composition:

  • 24% of the sample was smaller than 10 μm (aerosol)
  • 33% of the sample measured 10-50 μm
  • 20% of the sample measured  50-146 μm
  • 23% of the sample measured 146-294 μm
  • Source: IMO

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