Report on Krafla (Iceland) — July 1977
Natural Science Event Bulletin, vol. 2, no. 7 (July 1977)
Managing Editor: David Squires.
Krafla (Iceland) Continued inflation; significant increase in gas discharge
Please cite this report as:
Global Volcanism Program, 1977. Report on Krafla (Iceland). In: Squires, D. (ed.), Natural Science Event Bulletin, 2:7. Smithsonian Institution. https://doi.org/10.5479/si.GVP.NSEB197707-373080.
65.715°N, 16.728°W; summit elev. 800 m
All times are local (unless otherwise noted)
"Inflation in the central part of the Krafla caldera continues. The rate is 6-7 mm/day, similar to that of previous inflation periods. In the fault swarm S of the caldera (Námafjall), where maximum deformation occurred during the 27 April deflation, seismicity has decreased still further. Significant increase in gas discharge, accompanied by an increase in CO2, has taken place. So far, there are no signs that the activity in the Krafla area is decreasing."
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.