Report on Krafla (Iceland) — August 1979
Scientific Event Alert Network Bulletin, vol. 4, no. 8 (August 1979)
Managing Editor: David Squires.
Krafla (Iceland) Inflation slows; trigger level for previous deflations expected late October
Please cite this report as:
Global Volcanism Program, 1979. Report on Krafla (Iceland). In: Squires, D. (ed.), Scientific Event Alert Network Bulletin, 4:8. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN197908-373080.
65.715°N, 16.728°W; summit elev. 800 m
All times are local (unless otherwise noted)
"Krafla continues to inflate. As in many previous inflation periods, the rate of inflation as recorded in the Krafla power house was greatest during the weeks following the May deflation event. The rate then slowed, and during August was about 1 µrad/day, 1/3 of the initial rate. The ground level just prior to the May deflation event will at this rate be reached during the second half of October."
Geologic Background. The Krafla central volcano, located NE of Myvatn lake, is a topographically indistinct 10-km-wide caldera that is cut by a N-S-trending fissure system. Eruption of a rhyolitic welded tuff about 100,000 years ago was associated with formation of the caldera. Krafla has been the source of many rifting and eruptive events during the Holocene, including two in historical time, during 1724-29 and 1975-84. The prominent Hverfjall and Ludent tuff rings east of Myvatn were erupted along the 100-km-long fissure system, which extends as far as the north coast of Iceland. Iceland's renowned Myvatn lake formed during the eruption of the older Laxarhraun lava flow from the Ketildyngja shield volcano of the Fremrinamur volcanic system about 3800 years before present (BP); its present shape is constrained by the roughly 2000 years BP younger Laxarhraun lava flow from the Krafla volcanic system. The abundant pseudocraters that form a prominent part of the Myvatn landscape were created when the younger Laxarhraun lava flow entered the lake.
Information Contacts: K. Grönvold, NVI.