Mýrdalsjökull, (1,480 m) the fourth largest glacier in Iceland, about 701 km2. Many glacier tongues protrude from the main glacier towards Mýrdalssandur, such as Öldufellsjökull, Sandfellsjökull and Höfðabrekkujökull.

Under Mýrdalsjökull above Höfðabrekkujökull is the volcano Katla, which has erupted 16 times in the past 1,100 years, about once every 70 years or so.

The interval between eruptions varies from 40 to 80 years. The first recorded eruption was in 894 and the last one in 1918.

The eruptions usually start quite abruptly, sending torrents of melted glacier down across Mýrdalssandur, so huge they sweep away everything in their path.

Many farms have been destroyed and many lives lost in some of these floods.