Extent and economic significance of landslides in Denmark, Faroe Islands and Greenland

Denmark is not a country with a serious landslide problem, but several small landslides and a few large landslides occur sporatically. Almost all the landslides are in coastal cliff areas or in embankments and cuttings in a country characterized by lowlands with little relief. Landslides in Denmark can be classified into four types: rockfalls, rotational slides, mudslides, and mudflows. Rockfalls occur only in a very few, isolated localities. Rotational landslides and mudslides occur mainly in areas with highly to very highly plastic clays of Tertiary age lying at or close to the surface. The initial slide is rotational and subsequent movement is in the form of a mudslide or mudflow on the lower part of the original slide mass. Few data have been collected to evaluate the expenses arising from the landslides but the expenses are probably small. The total cost of repairing and preventing slides is estimated between 1 and 3 million US$ per year. This amount does not include the loss of land from erosion and associated landsliding. Landslides on the Faroe Islands are associated with clay within coal and lava of Tertiary age. All of the landsliding seems to have occurred in prehistoric time. Most of the landslides in Greenland are rockfalls caused by repeated freezing and thawing of Precambrian basement rocks. Mudflows in Neogene marine clay occur when the permafrost melts. Organic-rich shale of Cretaceous and Tertiary age have slid and apparently burned by spontaneous combustion. Minor damages to human facilities have been reported.