Geology
Exmoor is an upland of sedimentary rocks classified as gritstones, sandstones, slate, shale and limestone, siltstones, and mudstones depending on the particle size. They are largely from the Devonian and early Carboniferous periods (the name Devonian comes from Devon, as rocks of that age were first studied and described here). As this area of Britain was not subject to glaciation, the plateau remains as a remarkably old landform. Quartz and iron mineralisation can be detected in outcrops and subsoil. The Glenthorne area demonstrates the Trentishoe Formation of the Hangman Sandstone Group. The Hangman Sandstone represents the Middle Devonian sequence of North Devon and Somerset. These unusual freshwater deposits in the Hangman Grits, were mainly formed in desert conditions. The underlying rocks are covered by moors and supported by wet, acid soil. The highest point on Exmoor is Dunkery Beacon; at 519 metres (1,703 ft) it is also the highest point in Somerset.
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