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Steep Holm ((ウェールズ語:Ynys Rhonech), Old English: ''Ronech'' and later ''Steopanreolice'') is an English island lying in the Bristol Channel. The island covers at high tide, expanding to at mean low water. At its highest point it is above mean sea level. It lies within the historic boundaries of Somerset and administratively, it forms part of North Somerset. Between 1 April 1974 and 1 April 1996 it was administered as part of Avon. Nearby is Flat Holm island ((ウェールズ語:Ynys Echni)), part of Wales. The Carboniferous Limestone island rises to about and serves as a wind and wave break, sheltering the upper reaches of the Bristol Channel. The island is now uninhabited, with the exception of the wardens. It is protected as a nature reserve and Site of Special Scientific Interest (SSSI) with a large bird population and plants including wild peonies. There was a signal station or watchtower on the island in Roman times, but there may have been human habitation as early as the Iron Age. In the 6th century it was home to St Gildas and to a small Augustinian priory in the 12th and 13th centuries. An inn was built in 1832 and used for holidays in the 19th century. A bird sanctuary was established in 1931 and since 1951 has been leased to charitable trusts. It is now owned by the Kenneth Allsop Memorial Trust. In the 1860s the island was fortified with ten 7-inch rifled muzzle loaders as one of the Palmerston Forts for the coastal defence of the Bristol Channel until it was abandoned in 1898. The infrastructure was reused in World War I and II when Mark VII 6'' breech-loading guns and search lights were installed. To enable the movement of materials, soldiers from the Indian Army Service Corps initially used mules and then installed a cable-operated winched switchback railway. ==Geology and ecology== The island is formed of Carboniferous Limestone and is often described as geologically a continuation of the Mendip Hills at Brean Down, however the dip is at a different angle to that on Brean Down. On Steep Holm the dip is about 30 degrees to the north whereas at Brean Down it is 30 degrees to the south. There are some folds and fractures with dip angles up to 75 degrees created during the final phases of the Variscan orogeny near the end of the Carboniferous Period, 300 million years ago.〔(【引用サイトリンク】title=GCR block — Variscan Structures of South-West England )〕 The island rises to about from the surrounding sea and covers at high tide, whereas at low tide it expands to due to the tidal range of , second only to Bay of Fundy in Eastern Canada.〔(【引用サイトリンク】 title= Coast: Bristol Channel )〕〔(【引用サイトリンク】url=http://www.victorianforts.co.uk/pdf/datasheets/steepholm.pdf )〕 There are many caves on the island, and pot holes, up to deep, in the surrounding sea bed which are believed to be the remnants of collapsed cave systems. The caves on the islands cliffs are at two different levels, those in the current inter-tidal zone are below the water table and are producing stalactites, however many of the caves are situated high up on the cliffs which were on the water line many thousands of years ago. Steep Holm is protected as a nature reserve and Site of Special Scientific Interest (SSSI), notification having taken place in 1952. There is a large bird population, particularly European herring gulls ''(Larus argentatus)'' and Lesser black-backed gulls ''(Larus fuscus)''. There has also been a small population of muntjac deer. The plateau at the top of the island has a layer of soil between and deep. It has a red colour from veins of iron in the rock and has arrived as sand particles less than in diameter. The island is the only site in the UK on which wild peonies ''(Paeonia mascula)'' grow,〔(【引用サイトリンク】url=http://www.wildlifetrusts.org/who-we-are/history/rothschild-reserves/steep-holm-island-somerset )〕 although these have been damaged by the fungus botrytis.〔 The wild peony was introduced to the island of Steep Holm, possibly by monks, or brought from the Mediterranean by the Romans.〔(【引用サイトリンク】url=http://www.wanhs.org/SteepholmePeony.html )〕〔(【引用サイトリンク】url=http://www.martin-page.com/thepeonysociety.org/Steep_Holm.html )〕 Alexanders ''(Smyrnium olusatrum)'' are also common along with golden samphire, buck's-horn plantain ''(Plantago coronopus)'' and wild leeks ''(Allium ampeloprasum)''. The only reptiles on the island are slow worms ''(Anguis fragilis)''. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Steep Holm」の詳細全文を読む スポンサード リンク
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