Report on Krafla (Iceland) — February 1981
Scientific Event Alert Network Bulletin, vol. 6, no. 2 (February 1981)
Managing Editor: Lindsay McClelland.
Krafla (Iceland) Fissure eruption and intrusion end; inflation resumes
Please cite this report as:
Global Volcanism Program, 1981. Report on Krafla (Iceland). In: McClelland, L. (ed.), Scientific Event Alert Network Bulletin, 6:2. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN198102-373080.
65.715°N, 16.728°W; summit elev. 800 m
All times are local (unless otherwise noted)
"The initial vigorous phase of the eruption lasted until the early morning of 31 January. Then activity began to decrease, with shortening of the crater row that initially extended 2 km, then decreasing activity in the craters and declining lava production.
"The final activity in the craters died out just after 1400 on 4 February. During the eruption, slow deflation over the Krafla magma reservoirs, 8-9 km to the S, was observed, but inflation started again at about the same time as the eruption ceased. The lava covered 6.3 km2 and appeared to be similar in volume to the two previous eruptions in July and October 1980 (5:7,10).
"Considerable movement of faults extending about 1 km N of the main lava (~8 km N of the craters) was observed. Large volumes of steam emitted from these faults suggest that lava again forced its way down into the faults and then northward. Renewed earthquake activity in this region on 1 February was possibly associated with this fault movement.
"By early March the inflation of the magma reservoirs had regained over half of the deflation that accompanied the eruption. Experience indicates that previous ground levels will be reached about the end of March to early April."
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.