Porlock Vale has some of the best and most varied and interesting landscapes of the Exmoor National Park. Extending from Dunkery Beacon the highest point on Exmoor to Low Water Mark. The Bristol Channel has the second highest rise and fall of tide in the world, the highest is in the Bay of Fundy on the east coast of North America.
Bossington Hill on the east side of Porlock Vale, and Porlock Hill on the west side together with Dunkery afford excellent vantage points to view the landscape and follow changing light and vegetation patterns throughout the seasons.
The underlying rocks, how and where they were initially formed and how the rocks have weathered over the millennia materially influences the landscape.
The main rock of the upland area is Hangman Sandstone formation from the Devonian period (800-?1000m) purple, grey and green, fine to medium grained sandstone with reddish brown mudstone. Folded, fractured and cleaved. The higher area is part formed but largely open heather clad moorland with very few trees. The discontinuity of rocks at the East Lynch fault line shows Mercia Mudstone (c200m), Blue Anchor Formation (28.5m) Grey and green mudstone, with gypsum both from the Triassic period. Blue Lias Formation (up to 150m) from the Jurassic period. Grey mudstone and shale with thin limestones. Here some Ammonites have been found on farmland.
Below the moorland portion are the steep “scree” angular sandstone slopes mainly covered with sessile oak. In the lower sections is the Mercia Mudstone Group from the Triassic. Reddish brown mudstone with some sandstone.
Around the village of Luccombe are the Luccombe Breccia Formation (upto ?650m) causing the typical rounded topography.
In the lower parts of the Vale towards the coast are “Head”, river terrace deposits, salt marsh deposits, and storm beach gravel.
The Devonian Sandstone was first formed south of the Equator either in desert conditions or a shallow sea as a sedimentary rock, solidifying over time. Earth plate tectonics have caused the rocks to move from their created site to their present location.
Where active quarrying exists the underlying strata can be readily viewed, There are no operational quarries now; but in past years many small scale operations occurred. Often active for the duration of a building project, but hen unused until the next need. Many of the old stone buildings utilised stone from the beach, rivers and watercourses, discernible from the rounded feature of the stones, or from the many small quarries often exploited adjoining roads, lanes or tracks. The stone available was difficult to work to form quoins, and for important buildings imported stone was often used for quoins, door and window reveals. Also bricks have been incorporated for arches, quoins and reveals.
Often the easiest place to view local stone is in old buildings, bridges and boundary walls.
The red sandstone of Porlock Methodist Chapel came from a quarry at West Luccombe adjoining the access road to Burrowhayes Farm Camping Site.
Quarries in Hawkcombe and Horner Valley provided stone for local builders for many substantial structures.
Rarely, was stone of sufficient length and section available locally, and most old door and window lintels are therefore wooden.
For more detailed study and reference :
Exmoor Geology (Exploring the Landscapes, Rocks and Mines of the National Park) by R. A. Edwards
(ISBN 0 86183 411 9) Exmoor Books.
Copies obtainable at Porlock Visitor Centre
Sheet 278 and part of 294 Minehead (Solid & Drift Geology) 1:50,000 Series
British Geological Survey
Geological Survey of Great Britain Sheet 2
BGS information Office, natural History Museum, Exhibition road, London SW7 2DE