 It is also located over a deep-seated mantle plume known as the Iceland hotspot, which causes dynamic uplift of the Iceland Plateau, with associated volcanism and seismicity.The line of the Mid-Atlantic Ridge is offset by two transform zones in Iceland, the South Iceland Seismic Zone (SISZ) in the south and the Tjornes Fracture Zone in the north.The town of Hveragerdi is located at the western end of the SISZ, an area of considerable seismicity.