Changes at the surface of a volcanic edifice, such as snow or hydrological loading, ice cap melting, and flank destabilization, can cause significant surface deformation. Understanding the contribution of surface processes to ground deformation is therefore important for monitoring the state of the underlying volcanic system. The Katla Volcano in Iceland lies under Mýrdalsjökull, the fourth largest glacier in Iceland, and undergoes the largest seasonal deformation of all Icelandic volcanoes: up