Research paper
Multiple magma reservoirs in a rift zone volcano: Ground deformation and magma transport during the September 1984 eruption of Krafla, Iceland

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Abstract

Detailed study of rates and extent of ground deformation during and following the September 1984 eruption of the Krafla volcano, northeast Iceland, revealed the existence of several reservoirs that feed magma towards the volcano. A shallow magma reservoir - the Krafla magma reservoir - appears to be centered 2.6 km below the central part of the Krafla caldera. Three additional magma reservoirs, each displaying its own characteristic flow behavior, feed magma into the shallow reservoir. Reservoir I supplied very rapid flow during and immediately after the eruption. Reservoir II was the dominant supplier of magma 3 weeks to 4 months after the beginning of the 2 week long eruption. Reservoir III had dominated the supply of magma to the shallow reservoir for two years prior to the eruption. Reservoir I lies at a depth of less than 10 km and may be regarded as a smaller downward continuation of the shallow Krafla reservoir. Reservoir II appears to be deeper than 20 km and to have a volume roughly 5 times that of the shallow reservoir. Reservoir III lies at an indetermined depth, and its volume is immense.

The Krafla volcano started to deflate at about 20h20 on September 4, 1984, and the eruption commenced at 23h49 and continued until September 18. The lava covered a 24-km2 area, and its volume can be roughly estimated as 108 m3. About 20 million m3 of magma were emplaced as a dike, one meter thick and 8.5 km long, below the eruptive fissure. The deflation of the volcano as measured by the volume of the subsidence bowl, shows that 60–80 million m3 of magma escaped from the shallow magma reservoir immediately before and during the eruption.

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