(German: “sea of rock”), exposed rock surfaces that have been quickly broken up by frost action so that much rock is buried under a cover of angular shattered boulders. These mantles principally occur in Arctic regions and high mountain areas. Their continuity and depth varies with climate, vegetation, and rock type, but they may be as much as 4 metres (12 feet) deep. Felsenmeer are especially well developed on basalts and are consequently numerous on the Icelandic plateaus; they also develop quickly on sedimentary rocks and are widespread in the Canadian Arctic, extending to sea level.