Due to cirque erosion from two opposite directions the remains of the plateau form zig-zag lines in the longitudinal direction of the islands, which is particularly noticeable in the northern islands. There are lakes both in the low lying valleys and in the higher lying cirques. The lakes are the result of erosion by ice, water-filled eroded fractures, and in a few cases the damming up of bays with boulders or sand. The only sand dunes in the Faroes are at the south end of Sandsvatn, thus the lake at Sandur is one of the bays which is dammed up. The biggest lake, S rv gsvatn, on V gar is 6 km long.
Bogs occur on the floors and sides of the valleys and also in the high lying cirque valleys.
Today the largest area of bog is around the lake, Fjallavatn, on V gar. In recent years large stretches of bog have been flooded in the construction of reservoirs for the supply of electricity. A characteristic feature of the Faroese landscape are the deep, steep-sided ravines, which can be traced for kilometres as depressions in the terrain. They are formed by the erosion of fracture zones. There is a striking difference between the coastal forms in the sounds and fiords, on the east coast and those facing the north and west.