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A Tephrochronological DatabaseWelcome to the Tephrabase website Tephra layers (volcanic ash layers) are now an invaluable tool in palaeoenvironmental studies. The data produced by such research can be difficult to handle and disseminate. Tephrabase is a database of tephra layers found in Iceland, north-west and northern Europe, Russia and central Mexico. Details on the location, name, age and geochemistry of tephra layers are stored in the database, as well as information about relevant volcanoes and volcanic systems. A comprehensive reference database is also included. A new Laacher See supplementary data collection has been added. Eyjafjallajökull Eruption from the 20th March 2010![]() MODIS Terra satellite image of the plume heading towards Shetland, taken at 11.35 GMT 15th April 2010. (Image NASA/GSFC, MODIS Rapid Response) Volcanic activity switched to Eyjafjallajökull's main crater just after midnight on the 14th April. After several weeks of relatively mild fissure activity in the Fimmvörduhals area, which resulted in lava flows and scoria cone creation, the main crater of Eyjafjallajökull began erupting early on the 14 April. This subglacial eruption has resulted in several jökulhlaups (large floods of melted ice) which have flowed north out of Gígjökull into the Markarfljót valley. The flood waters have flooded farmland and some properties, as well as damaging roads and bridges. In preparation holes were made in the route 1 embankments in an effort to save the main road bridge across the Markarfljót. Further flooding can be expected as long as the eruption is melting ice in Eyjafjallajökull's main crater. Although Eyjafjallajökull continues to pump ash into the atmosphere, much of Europe's airspace was reopened on 20 April. This largely reflected a change in the regulators' view on the tolerance of jet engines to low concentrations of tephra. The eruption has varied considerable over the past week, with a lava flow extending northwards beneath Gígjökull. This has contributed to continued meltwater being created. The explosivity of the eruption has also varied, with an increase in plume height to around 9 km reported by Institute of Earth Sciences/Nordic Volcanological Institute on the 6th May. Winds were carrying the tephra to the south of Iceland. The large amounts of tephra being produced by the eruption are a result of the interaction between the lava and the glacier which overlies the volcano. The erupting magma melts the overlying ice, creating steam, and it is the rapid explosive expansion of the ice to steam which literally blows the molten lava into fine ash fragments (very similar to what happens if you pour water onto an oil fire). This type of activity (phreatomagmatic) is typical of Iceland's subglcial volcanoes and is responsible for Iceland having a fantastic record of past eruptions in its soils. This is why Iceland is probably the best place in the world to use tephrochronology (use of tephra layers for dating).
Eyjafjallajökull burst into life after nearly 190 years of inactivity (1821-1823) on the 20th March. Fljótshlíd residents noticed an orange glow on the edge of the volcano at 23:52 GMT. The initial eruption was in the Fimmvörduhals area, the pass between Eyjafjallajökull and Mýrdalsjökull, and produced alkali-olivine basaltic lava with an SiO2 content of around 47% according to the Institute of Earth Sciences/Nordic Volcanological Institute. Activity decreased over time until the fissure eruption stopped on the 12th April. Analyses of the tephra from the second phase of activity show a more evolved source, with an SiO2 content of around 58% with a high fluorine content. With activity switching to the main crater of Eyjafjallajökull on the 14th April, concerns will grow about neighbouring Katla (last eruption 1918), beneath Mýrdalsjökull. In the past, activity in Eyjafjallajökull has been accompanied by eruptions of Katla. For example, the last activity (1821-1823) at Eyjafjallajökull saw an eruption of Katla in 1823. An eruption of Katla, if it occurs will probably result in more intense activity and larger jökulhlaups than the current Eyjafjallajökull eruption. The Institute of Earth Sciences/Nordic Volcanological Institute at the University of Iceland are the main group who are monitoring the eruption.
Further details on the eruption can be found via these links:
The Fimmvörduhals Eruption
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