domingo, abril 11, 2010

Continua a erupção do Eyjafjallajökul na Islândia

Eruption in Iceland at the Eyjafjallajökull volcanic system begins 20 March 2010

An eruption began in South Iceland in late evening of 20 March 2010 at the Eyjafjallajökull volcanic system (also known as Eyjafjöll volcano - Global Volcanism Program Volcano number 1702-02=). The initial visual report of the eruption was at 23:52 GMT, when a red cloud was observed at the volcano, lightening up the sky above the eruptive site. The eruption was preceded with intense seismicity and high rates of deformation in the weeks before the eruption, in association with magma recharging of the volcano. Immediately prior to the eruption the depth of seismicity had become shallow, but was not significantly enhanced from what it had been in the previous weeks. Deformation was occurring at rates of up to a centimetre a day since March 4 at continuous GPS sites installed within 12 km from the eruptive site.

The eruption broke out with fire fountains and Hawaiian eruptive style on about 500 m long NE-SW oriented eruptive fissure at N63º 38.1′, W19º 26.4′ on the northeast shoulder of the volcano at an elevation of about 1000 m. It was observed from air from 4-7 A.M. on March 21. Lava flows short distance from the eruptive site, and minor eruption plume at elevation less than 1 km was deflected by wind to the west. Volcanic explosive index (VEI) is 1 or less. Tephra fall is minor or insignificant.

The eruption occurs just outside the ice cap of Eyjafjallajökull, and no ice melting is occurring at present.

Satellite data is being used to study the eruption and associated intrusion. Several MODIS thermal images on 21 March show a temperature anomaly where the eruption is occurring. ENVISAT ASAR images before and during the eruption have been acquired, and a series of TerraSAR-X images cover the area.


The eruption is located on about 2 km wide pass of ice-free land between Eyjafjallajökull and the neighbouring Katla volcano with its overlying Myrdalsjökull ice cap. Katla volcano is known for powerful subglacial phreatomagmatic eruptions producing basaltic tephra layers with volumes ranging from ~0.01 to more than 1 cubic kilometer.

Three previous eruptions of Eyjafjallajökull are known in the last 1100 years (historical time in Iceland). The most recent began in December 1821 and lasted intermittently for more than a year. The neighbouring volcano Katla erupted then on 26 June 1823. Other eruptions include an eruption in 1612 or 1613, and about 920 A.D.

Episodes of unrest are known at Eyjafjallajökull, with documented sill intrusions in 1994 and 1999.


  • Freysteinn Sigmundsson (, Magnus Tumi Gudmundsson (, Gudrun Larsen (, Sigrun Hreinsdottir (, Páll Einarsson (, Ingibjörg Jónsdóttir ( - Nordic Volcanological Center, Institute of Earth Sciences, University of Iceland
  • Steinunn Jakobsdóttir (, Kristin S. Vogfjord (, Sigurlaug Hjaltadottir (, Gunnar B. Gudmundsson ( - Icelandic Meteorological Office, Reykjavik, Iceland.
Fonte: OVGA

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