Mendips header
 
 Home
 Overview maps
 Locality areas
  Cheddar Gorge
 Charterhouse
 Blackdown
 Burrington Combe
 Shipham & Rowberrow
 Crook Peak & Axbridge
 Banwell to Churchill
 Priddy
 Harptree & Smitham Hill
 Draycott & Westbury-sub
 -Mendip
 Wookey Hole & Ebbor
 Gorge
 Wells
 Great Elm & Vallis Vale
 Mells & the Wadbury Valley
 The Vobster area
 The Whatley area
 Torr Works & Asham Wood
 Beacon Hill
 Stoke St Michael & Oakhill
 Holwell & Nunney
 Shepton Mallet & Maesbury
 Gurney Slade & Emborough
 The Nettlebridge valley
 Geology
 Rocks of Mendips
 Fossils
 Geological timescale
 Ancient environments
 Geological structure
 Minerals and mines
  Minerals and mines
 Industrial archaeology
 Quarrying
  Stone as a resource
 Employment & the economy
 Quarrying & geodiversity
 Quarrying & the environment
 History of quarrying
 Caves and karst
 How caves form
 Dry valleys and gorges
 Dolines and sinkholes
 Mendip caves
 Going caving
 Hydrogeology
 Biodiversity
  Flora and fauna
 Typical Mendip habitats
 Special Mendip habitats
 Horseshoe bats
 Appendix of names
 Biodiversity of western
 Mendip
 Biodiversity of eastern
 Mendip
 External links
 Detailed site information
  Coal mining
  Mendip quarry companies
  East Mendip quarries
 Biodiversity of eastern
 Mendip
  West Mendip quarries
 Biodiversity of western
 Mendip
 Acknowledgements
 Site map
Beacon Hill
Beacon Hill is the highest point on eastern Mendip, and forms a broad north-west-trending ridge which marks the axis of the Beacon Hill Pericline. The Devonian Portishead Formation and older Silurian volcanic rocks (Coalbrookdale Formation) outcrop in the core of the pericline, with the Carboniferous Limestone flanking both sides, although in places the limestone is buried beneath younger rocks.

At the top of Beacon Hill is a narrow strip of woodland managed by the Woodland Trust in which are a few small outcrops of the Portishead Formation. South of the wood, there is a prominent break of slope, which marks the margin of the Lower Jurassic Downside Stone outcrop. This younger rock is draped over the older Carboniferous and Devonian rocks, and forms a gently sloping plateau between here and Shepton Mallet. To the east, the Silurian Coalbrookdale Formation volcanic rocks outcrop along the ridge. They consist of andesite and rhyodacite lavas, tuffs (consolidated volcanic ash) and agglomerate (volcanic conglomerate) sandwiched between ash-rich, fossiliferous siltstone and mudstone.

Fragments and pebbles of these rocks can be seen in ploughed fields and stone walls across the outcrop.

At the eastern end of the ridge lies Cranmore Tower, a folly built by local landowner Sir Richard Paget in 1863. The tower is not open to the public, but there is a good view across to the Cretaceous Upper Greensand escarpment and the conspicuous knoll of Cley Hill from the surrounding fields. Cley Hill is an outlier of Upper Cretaceous Chalk, with the main Chalk mass of Salisbury Plain beyond. To the north-east, the Westbury White Horse sits just east of the conspicuous chimney of the Westbury Cement Works.

  Aerial view of Beacon Hill (click to enlarge view).

Aerial view of Beacon Hill (click to enlarge view).

Cross section of a volcano similar to that which erupted here 420 million years ago

Quarrying
The Silurian volcanic rocks have been quarried at Moon's Hill Quarry, south of Stoke St Michael for over 120 years. This site comprises two clearly visible large pits situated on either side of the road. The two quarries are now operated as a single entity by John Wainwright & Co. Ltd.. It is a working quarry, so access is only by prior arrangement.

  The volcanic rocks were also quarried just south of Tadhill at Downhead Quarry. Just over a kilometre south of Moon's Hill Quarry is the disused and now water filled Waterlip Quarry which worked the Carboniferous Black Rock Limestone. The rock was transported to the railway at Cranmore Station by a tramway, which also served Moon's Hill Quarry and Downhead Quarry, 3 km to the north-east.
Silurian volcanic rocks exposed in Moon's Hill Quarry

goto the British Geological Survey home page