Report on Grimsvotn (Iceland) — 15 January-21 January 2014
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 15 January-21 January 2014
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2014. Report on Grimsvotn (Iceland). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 15 January-21 January 2014. Smithsonian Institution and US Geological Survey.
64.416°N, 17.316°W; summit elev. 1719 m
All times are local (unless otherwise noted)
According to the Icelandic Meteorological Office, the level of the Skaftá river at Sveinstindur and electrical conductivity both rose during 18-19 January indicating a glacial outburst flood (jokulhlaup), originating from Grímsvötn's western Skaftá ice cauldron. The jokulhlaup was unconfirmed without visual observations, however. Flood waters peaked on 20 January and then began to subside on 21 January. The report noted that floods in Skaftá source from two ice cauldrons formed by persistent geothermal activity beneath Vatnajökull. The cauldrons drain an average every two years, producing floods of up to 1,500 cubic meters per second.
Geologic Background. Grímsvötn, Iceland's most frequently active volcano in historical time, lies largely beneath the vast Vatnajökull icecap. The caldera lake is covered by a 200-m-thick ice shelf, and only the southern rim of the 6 x 8 km caldera is exposed. The geothermal area in the caldera causes frequent jökulhlaups (glacier outburst floods) when melting raises the water level high enough to lift its ice dam. Long NE-SW-trending fissure systems extend from the central volcano. The most prominent of these is the noted Laki (Skaftar) fissure, which extends to the SW and produced the world's largest known historical lava flow during an eruption in 1783. The 15-cu-km basaltic Laki lavas were erupted over a 7-month period from a 27-km-long fissure system. Extensive crop damage and livestock losses caused a severe famine that resulted in the loss of one-fifth of the population of Iceland.