". . . The ground level at which previous deflation events and eruptions were triggered was again reached about 10 January, but inflation continued.

"On 30 January at about 0700, slow deflation of the magma reservoirs started, as recorded by tiltmeters at the Krafla power plant. The rate of deflation rapidly increased and at about 0730 tremor appeared on seismometers. Deflation rate and tremor amplitude reached a maximum at about 0900 and declined very gradually thereafter. The earthquake epicenters indicated movement of magma along the fault swarm toward the N. Soon after 1400, a fissure eruption started in the fault swarm 8-9 km N of the center of the magma reservoirs. The fissure soon extended to 2 km length and the lava front quickly moved toward the N. The eruption site was close to those of July and October, 1980 and the eruptive behavior was broadly similar. In the morning of 31 January, the fissure had shortened to about 300-400 m and the lava production rate had decreased somewhat.

"The eruption and very slow deflation were continuing on 2 February. The eruption site is in an uninhabited area and poses no danger to the local population. Observations are hampered due to remoteness and difficult weather conditions."

Geological Summary. 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; P. Einarsson, Univ. of Iceland.