Global Volcanism Program | Image GVP-05992
Askja's largest historical eruption occurred in 1875. Subsidence of the caldera continued for 40-50 years after the eruption and resulted in the formation of Askja's inner caldera, now filled by Öskjuvatn lake, seen here from the SE. The flat, lava-covered floor of the main caldera can be seen beyond the lake, encircled by the caldera rim.
Photo by Michael Ryan, 1984 (U.S. Geological Survey).