Grímsvötn volcano
Status Report: 16:00 GMT, 25 May 2011
Icelandic Meteorological Office and Institute of Earth Sciences, University of Iceland
Compiled by:
Gunnar B. Guðmundsson and Sigrún Hreinsdóttir with input from
Hrafn Guðmundsson, Árni Sigurðsson, Þórður Arason, Sigurlaug
Hjaltadóttir, Þóranna Pálsdóttir, Matthew J. Roberts, Gunnar
Sigurðsson, Björn Oddsson, Ingibjörg Jónsdóttir, Ármann Höskuldsson
and Páll Einarsson.
Based on:
IMO seismic monitoring; IES-IMO GPS monitoring; IMO
hydrological data; weather radar; ash-fall reports; scientific overflights;
UK Met Office ATDnet; MODIS and NOAA satellite images.
Eruption plume:
Height (a.s.l.):
Yesterday evening until 20:00 UTC, the ash plume did not reach
higher than 5 km, but after that there were frequent pulses to 5-7 km.
At 02:00 UTC the plume reached 12 km height, but after 2:20 UTC the
plume has not been detectable on radar, except for an steam plume at
3:30 UTC, which reached 5 km. Eyewitnesses have reported small
steam bursts from the crater today. Widespread ash in cloud layers
have been detectable from plane between 5-7 km W of the volcano and
also some ash haze below 3 km SW of the eruption site.
Heading:
Light north-easterly winds, but calm winds last night and today. South-
east and southerly winds above 4 km.
Colour:
Light-brown.
Tephra fallout:
Only in the vicinity of the eruption site.
Lightning:
Two lightning strikes were detected yesterday at 21:02 UTC and 12
lightning strikes between 02:09-02:19 UTC today.
Noise:
No noise from the volcano has been reported.
Meltwater:
According to satellite images very little ice has melted during the
eruption. No signs of flooding is detected.
Conditions at eruption site:
Yesterday evening there was still active explosivity in Grímsvötn. The
activity is in three to four tephra cones surrounded by meltwater. The
activity is pulsating with explosions producing ash clouds that rise up
from the craters, some reaching a few km. The eruption plume is not
continuous and all the material falls out nearby.
Seismic tremor:
Seismic tremor level at the Grímsfjall station lowered yesterday
evening between 21:15 - 21:45 UTC. At about 02 UTC today the
tremor decreased considerably and has been fairly stable since.
Earthquakes:
No earthquakes were recorded in the volcano today.
GPS deformation:
No significant displacement was observed at the GPS-station at Mt.
Grimsfjall yesterday.
Overall assessment: All measurements and aerial observations show that the eruption has
diminished substantially. Ash-fall is now confined to the vicinity of the
eruption site.
Details in
status report issued collectively by the Icelandic Meteorological Office and the Institute of Earth Sciences
