Hofsjökull volcano lies along an east-west-trending area connecting the two principal rift zones of Iceland. It bridges the gap between the Reykjanes-Langjökull rift on the west, which terminates at Langjökull, and the eastern zone, which extends NE-ward across east-central Iceland. The roughly 7 x 11 km central caldera lies beneath the western part of the massive Hofsjökull icecap. A small Holocene shield volcano is located at the SW margin of the icecap. Flank fissures north and east of the icecap have produced basaltic lava flows during the Holocene. Kerlingarfjöll, a glacially dissected, largely Pleistocene rhyolitic central volcano located SW of the Hofsjökull icecap, is considered part of this volcanic system. Steep-sided Pleistocene rhyolitic lava domes and numerous hot springs occupy two calderas at the center of the 5 x 7 km wide complex. Fumarolic activity at Kerlingarfjöll, mostly concentrated in the center of the complex, is the most vigorous in Iceland.