Natural Hazards 31: 277–287, 2004. © 2004 Kluwer Academic Publishers. Printed in the Netherlands. 277 Landslide and Tsunami 21 November 2000 in Paatuut, West Greenland TRINE DAHL-JENSEN 1⋆ , LOTTE MELCHIOR LARSEN 1 , STIG A. SCHACK PEDERSEN 1 , JERRIK PEDERSEN 2 , HANS F. JEPSEN 1 , GUNVER KRARUP PEDERSEN 2 , TOVE NIELSEN 1 , ASGER KEN PEDERSEN 2 , FRANTS VON PLATEN-HALLERMUND 1 and WILLY WENG 1 1 Geological Survey of Denmark and Greenland, Geocenter Copenhagen, Denmark; 2 University of Copenhagen, Geocenter Copenhagen, Denmark (Received: 14 August 2002; accepted 23 January 2003) Abstract. A large landslide occurred November 21, 2000 at Paatuut, facing the Vaigat Strait on the west coast of Greenland. 90 million m 3 (260 million tons) of mainly basaltic material slid very rapidly (average velocity 140 km/h) down from 1,000–1,400 m altitude. Approximately 30 million m 3 (87 million tons) entered the sea, creating a tsunami with an run-up height of 50 m close to the landslide and 28 m at Qullissat, an abandoned mining town opposite Paatuut across the 20 km wide Vaigat strait. The event was recorded seismically, allowing the duration of the slide to be estimated to circa 80 s and also allowing an estimate of the surface-wave magnitude of the slide of 2.3. Terrain models based on stereographic photographs before and after the slide made it possible to determine the amount of material removed, and the manner of re-deposition. Simple calculations of the tsunami travel times are in good correspondence with the reports from the closest populated village, Saqqaq, 40 km from Paatuut, where refracted energy from the tsunami destroyed a number of boats. Landslides are not uncommon in the area, due to the geology with dense basaltic rocks overlying poorly consolidated sedimentary rocks, but the size of the Paatuut slide is unusual. Based on the observations it is likely at least 500 years since an event with a tsunami of similar proportions occurred. The triggering of the Paatuut slide is interpreted to be caused by weather conditions in the days prior to the slide, where re-freezing melt water in pre-existing cracks could have caused failure of the steep mountain side. Key words: Landslide, tsunami, run-up height, cause of landslide, seismic record of landslide 1. Introduction Mid afternoon November 21, 2000, the population in the small fishing village of Saqqaq on the central west coast of Greenland were frightened by a series of large, strange waves washing up the shore overturning and crushing boats among bergy bits of ice. In the ensuing panic, a distress signal was reported to the local police in Ilulissat, who the following day when daylight returned commissioned a SAR mission by helicopter. It turned out that nobody was in distress and nobody was hurt, but the probable cause was found – a large landslide had occurred at Paatuut, ⋆ Author for correspondence. E-mail: tdj@geus.dk