Report on Krafla (Iceland) — May 1989
Scientific Event Alert Network Bulletin, vol. 14, no. 5 (May 1989)
Managing Editor: Lindsay McClelland.
Krafla (Iceland) Four years of inflation interrupted by deflation
Please cite this report as:
Global Volcanism Program, 1989. Report on Krafla (Iceland). In: McClelland, L (ed.), Scientific Event Alert Network Bulletin, 14:5. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN198905-373080.
65.715°N, 16.728°W; summit elev. 800 m
All times are local (unless otherwise noted)
Krafla last erupted in September 1984 (9:8 and 10-11) and slow, intermittent inflation has been recorded since early 1985. Tilt records (figure 12) show three inflationary pulses since January 1988. Each lasted 2-3 months and was accompanied by increased seismicity. The inflation rate was generally 1-2 mm/day at the center of deformation, indicating a magma flow rate of ~1 m3/s into Krafla's shallow magma reservoir. Slow deflation was observed March-May 1989, accelerating 20-30 May to a rate similar to the previous inflation. No unusual seismicity or surface activity was associated with the deflation.
|Figure 12. North component of tilt recorded January 1988-May 1989 at the Krafla power station, ~1.5 km S of the center of the deformation. Inflation is uplift toward then N. Courtesy of Eysteinn Tryggvason.|
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: E. Tryggvason, NVI.