such as a larger earthquake, a large mass added near a slope, or an abnormal rainfall which leaves the topsoil fully saturated so that additional water has nowhere to permeate except into the clay — can disturb the clay and initiate the process of liquefaction. Disasters Because the clay layer is typically covered with topsoil, a location which is vulnerable to a quick clay landslide is usually identifiable only by soil testing, and is rarely obvious to a casual observer. Thus human settlements and transportation links have often been built on or near clay deposits, resulting in a number of notable catastrophes: In 1702, a landslide destroyed almost all traces of the medieval town Sarpsborg in the Viken county in Norway. 15 people and 200 animals were killed. On 19 May 1893, a landslide in Verdal, Norway, killed 116 people and destroyed 105 farms. It left a crater several kilometers in diameter. The most disastrous such landslide to affect North America occurred in 1908, when a slide into the frozen Du Lièvre River propelled a wave of ice-filled water into Notre-Dame-de-la-Salette, Quebec, causing the loss of 33 lives and the destruction of 12 homes. In 1955, a landslide affected part of the downtown of Nicolet, Quebec, causing $10 million in damages. In 1957, a large quick-clay landslide occurred in Lilla Edet, by the Göta River, in southwestern Sweden. A large part of a factory slid into the river, causing a thirty meter reduction in the river width. The earth mass coming into the river produced an approximately six meter high wave. On March 27, 1964, parts of Anchorage, Alaska built on sandy bluffs overlying "Bootlegger Cove clay" near Cook Inlet, most notably the Turnagain neighborhood, suffered landslide damage during the 1964 Alaska Earthquake. The neighborhood lost 75 houses in the landslide, and the destroyed area has since been turned into Earthquake Park. On 4 May 1971, 31 lives were lost when 40 homes were swallowed in a retrogressive flowslide in Saint-Jean-Vianney, Quebec, resulting in the relocation of the entire town when the government declared the area uninhabitable due to the presence of Leda clay. The event at Saint-Jean-Vianney contributed to the abandonment of the town of Lemieux, Ontario, in 1991, after a 1989 study showed it was also located on the same type of clay along the South Nation River. In 1993, those findings were borne out when the town's