Karst terrain. Artwork of surface features that occur in a typical temperate karst landscape. Although resistant to physical weathering, karst rock, usually limestone or dolomite, can be dissolved by mildly acidic water. This weakness gives rise to landform features particular to karst systems. In general, rock outcrops in these systems are highly dissected and rivers and streams frequently disappear beneath ground and reappear as springs (bottom left). The circular depressions at top are sink holes, areas where the surface bedrock has been removed by water. Such holes may form the entrance to a cave beneath ground. The bare, exposed areas of surface rock above the cliffs (lower centre) formed by glacial erosion. They are known as limestone pavement.