Map of Mýrdalsjökull and surrounding geology. The inferred calderahas been marked in. Other features typical of a large central volcano are the rhyolitic rocks. The Katla jökulhlaup floods emerge under and over the Kötlujökull glacier east of the main Mýrdalsjökull glacier. The seawards protrusion of the coastline at bottom right (Kötlutanga) is the result of sand deposition during the 1918 eruption, when Mýrdalssandur was covered in flood water and icebergs, which also floated in the sea.

(Map from Geological map of Iceland, sheet 6, Museum of Natural History and The Icelandic Geodetic Survey, Reykjavík, with permission.)