Hard and smooth pinkish brown sandstones generally underlie much of the northern part of Exmoor moor, with grey flaky shales and slates covering much of the area to the south (Edmonds and Williams 1985; Edwards 1999, 2000). This geological structure is broadly reflected in the topography consisting of two principal west-east ridges: one running along the coast and a central ridge that includes the highest land, The Chains and the highest point at 519 m, Dunkery Beacon (Figure 7.1). Replicating the geological axes, a watershed runs roughly east-west across this part of the moor. Rivers or streams flowing north do so swiftly, sometimes through rocky gorges, for only short distances to the northern coast. The local term for these is ‘water’—for example, Farley Water, Hoaroak Water, Badgworthy Water-which infers that they are too small to be properly called rivers and too large and powerful to be referred to as streams, flowing as they do in very deeply incised valleys created in ancient periglacial conditions (Straw 1995). There are some thirty named rivers and

waters marked by the Ordnance Survey crossing Exmoor averaging about 10 miles in length making a total of 300 miles of significant watercourses together with hundreds more miles of unnamed streams and tributaries (Allen 1978; Bonham-Carter 1991: 81). The rivers flowing south generally have less steep gradients and wind through the confined flat valley bottoms in which alluvial sediments have built up over millennia. The rivers are far longer, connecting the moor with the English Channel. The moor is named after the river Exe, which rises in its centre before flowing south to reach the sea beyond Exeter in East Devon (see Chapter 6). This dual directionality makes Exmoor distinctive both in terms of its own geography and its riverine and coastal connectedness to the outside world.