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) (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."
Geological Summary. The Krafla volcanic system in the Northern Volcanic Zone (NVZ) of Iceland is about 100 km long, consisting of a fissure swarm and a central volcano with a 7 x 9 km caldera formed about 110,000 years ago that deposited a rhyolitic welded tuff. It has been moderately active in the Holocene, over three distinct eruptive periods; the current one has lasted about 2,800 years with six volcano-tectonic episodes, each with one or more basaltic fissure eruptions. Lava volumes (DRE) have been in the 0.1-1 km3 range. The Hverfjall and Ludent tuff rings east of Myvatn were erupted along the fissure system. Myvatn lake formed during the eruption of the older Laxarhraun lava flow from the Ketildyngja shield volcano of the Fremrinamur volcanic system about 3,800 years before present (BP); The present Myvatn lake is constrained by the roughly 2,000 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. The last eruption took place in 1975-1984 CE when nine small basaltic fissure eruptions produced 0.25 km3 of lava.
Information Contacts: K. Grönvold, NVI.