Long Mountain (Powys)
hill (408m) in Powys
Long Mountain (Welsh: Cefn Digoll) is a hill straddling the boundary between Powys (Wales) and Shropshire (England) to the east of Welshpool though the summit at 408 metres (1,339 feet) at Beacon Ring (grid reference SJ265058) is within Wales. Long Mountain is a Marilyn (a hill with topographic prominence of at least 150 metres), having a prominence of 305 metres (1,000 feet).
Geology
Long Mountain is formed from a succession of sedimentary rocks dating from the Silurian period. In stratigraphic order i.e. youngest/uppermost first, these are:
Raglan Mudstone Formation (siltstone, mudstone)
Temeside Mudstone Formation (mudstone, siltstone, sandstone)
Tilestones Formation (sandstone)
Cefn Einion Formation (mudstone, siltstone, sandstone)
Knucklas Castle Formation (mudstone, siltstone, sandstone)
Bailey Hill Formation (siltstone, sandstone) (including the Cwm-yr-hob Member (mudstone, siltstone, sandstone)
Irfon Formation (mudstone, siltstone)
Gyfenni Wood Shale Formation (mudstone)
Trewern Brook Mudstone Formation (mudstone) (including the Mottled Mudstone Member)
Tarannon Mudstone Formation (mudstone)
Cefn Formation (mudstone, sandstone)
The first three listed above form a part of the Old Red Sandstone sequence and occur only in the easternmost part of the area. The summit which is towards the southwestern end of Long Mountain is formed by rocks of the Knucklas Castle Formation. Numerous faults cut the succession. There are a number of glaciofluvial deposits around the margins of Long Mountain, dating from the last ice age. Pockets of glacial till of similar age occur in some of the valleys.
Geography
Long Mountain extends from Forden, Powys, in the southwest to Vennington near Westbury in Shropshire to the northeast.
“Long Mountain (Powys)” enters the record as hill (408m) in Powys. Crown Archives preserves that source wording while asking what Long, Mountain and Powys can confirm, complicate or overturn.
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This entry incorporates text from “Long Mountain (Powys)” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.