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| geology = Carboniferous limestone | entrance_count = 2 | entrance_list = | difficulty = | hazards = | access = | show_cave = 1935〔 | show_cave_length = | lighting = Electric | visitors = | features = | survey = Trevor D. Ford, 1954 | survey_format = | website = }} Treak Cliff Cavern is a show cave near Castleton in Derbyshire, England. It is part of the Castleton Site of Special Scientific Interest and one of only two sites where the ornamental mineral Blue John is still excavated (the other is the nearby Blue John Cavern).〔 As part of an agreement with English Nature, the Blue John that can be seen in the show cave is not mined but it is extracted in small quantities from other areas of the cave and made into saleable items like bowls, jewellery and ornaments.〔(【引用サイトリンク】title=All about us )〕 The cave comprises two sections, the Old Series, discovered by lead miners in the 18th century, and the New Series, discovered during blasting in the 1920s. Only the Old Series contains Blue John, but the New Series is well decorated with flowstone, stalagmites and stalactites. Three human skeletons and flint implements from the Neolithic era were found in a small cave nearby in 1921.〔 ==Geology== Treak Cliff, the hill in which the cavern lies, is composed of Carboniferous Limestone; the steep eastern slope of the hill is thought to have been the edge of a reef on the margin of a tropical lagoon. This reef was then raised above sea level by an uplift in the Earth's crust and was subsequently eroded, forming a boulder bed on the slopes. This was subsequently overlain by deltaic river sediments, which formed the shale and Millstone Grit sandstones that still overlay the limestone to the north, and on top of those the Coal Measures formed, until the limestone was deep beneath the surface and subject to high temperature and pressure. Major earth movements at the end of the Carboniferous period reversed this subsidence, and the rock layers were raised to form an anticline, the top of which was eroded away. Surface streams, on meeting the limestone, percolated through cracks and weaknesses and started to dissolve the limestone to form caverns. The stream that formed the New Series once flowed into the lower end of Winnats Pass, whereas the stream that formed the Old Series lost its headwaters to the predecessor of the modern Odin Sitch as it cut down through soft shales. There is no modern stream in the Treak Cliff Cavern, but percolating water from the cave has been dye-tested and found to emerge at the Russet Well beside Peakshole Water near Peak Cavern in Castleton, taking between 13 and 20 hours to travel the distance.〔 Since their original formation, the caverns have been decorated by the formation of flowstone, stalagmites and stalactites. Two stalagmite samples from the Aladdin's Cave section of the Treak Cliff Cavern have been found, by means of radioactive dating, to date back 111,000 years, proving the cave itself is much older. The formations in Treak Cliff are variously stained orange or red by iron, white by lead and occasionally green or blue by copper. Some of the stalactites have been distorted by variations in the flow to form twisted structures known as helictites.〔 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「Treak Cliff Cavern」の詳細全文を読む スポンサード リンク
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