As of 10 June, slow inflation continued at Krafla. Dartmouth College geologists visited Iceland 11-19 May and measured SO₂ emissions with the cooperation of NVI personnel. At Krafla, SO₂ was remotely monitored by COSPEC in the Leirhnjúkur area WNW of Krafla, where the October 1980 fissure eruption occurred (5:10). Significant concentrations of SO₂ were directly detected in the area of the January 1981 eruption fissures. The COSPEC detected SO₂ north and SW of Hekla's April 1981 lava flows.

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; R. Stoiber and S. Williams, Dartmouth College.