The Snæfellsjökull volcanic system has been moderately active in the Holocene. The last eruption was a small basaltic eruption less than 1800 years ago, the lava covering about 4.5 km2.
The 30 km long and up to 20 km wide volcanic system lies on the Snæfellsnes Volcanic Zone and consists of a central volcano rising to 1446 m and a westward trending fissure swarm. The central volcano has a small ice cap covering a 2.5 km wide caldera or summit crater.
The characteristic activity is effusive basaltic eruptions and infrequent explosive silicic eruptions followed by extrusion of intermediate lava. Volumes of silicic tephra are poorly known but are probably in the range 0.2-0.5 km3.
Eruption frequency during the last 11.000 years is about 1 eruption per 400 years on average. Eruptions at the summit crater are accompanied by jökulhlaup, a flood of meltwater.