Mýrdalssandur is an outwash plain on the south coast of Iceland.
The outwash plain was built by the numerous jökulhlaups of the Mýrdalsjökull. The last large jökulhlaup was due to an explosive eruption of the Katla volcano under the glacier in 1918

A jökulhlaup (literally "glacial run") is a type of glacial outburst flood. It is an Icelandic term that has been adopted in glaciological terminology