By Gunver Krarup Pedersen, University of Copenhagen
In Disko and Nuussuaq the Cretaceous and Paleocene sediments are overlain by a thick pile of dense volcanic rocks, and steep slopes are prone to failure. Slides and avalanches are well-known from the south coast of Nuussuaq. If organic-rich shales or mudstones are involved in slides the slide may initiate an exothermal oxidation of organic matter and pyrite. This self-combustion may reach high temperatures. The burnt shales or mudstones change colour. The original dark grey to black shales turn pink. The pink colour reflects the loss of organic matter and the oxidation of Fe-bearing minerals.