The rocky uplands were flattened to a tablelike surface by ancient erosional activity. This tableland was subsequently elevated and now lies above the coastal plain and the ocean. The escarpment, where the tableland falls away to the coastal plain, is known as the Long Mountains.
It is into the edge of this table of rock that glaciers cut, forming the typical steep-sided U-shaped valeys and fjords (where connected to the sea) or fjord lakes (where blocked off at the seaward end, so the water is fresh). These glacial valleys form some of the most scenic vistas on the western edge of the Northern Peninsula.