Giant canyon passage (Audubon Avenue, Mammoth Cave, Kentucky, USA) 5 : 無料・フリー素材/写真
Giant canyon passage (Audubon Avenue, Mammoth Cave, Kentucky, USA) 5 / James St. John
| ライセンス | クリエイティブ・コモンズ 表示 2.1 |
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| 説明 | Western Kentucky's Mammoth Cave is the longest cave system on Earth, with 412 miles known and mapped. The name does not refer to the early discovery of fossil mastodon or mammoth bones here. Rather, the name refers to the immense size of many rooms and passages. The system is famous for having giant canyon passages. Canyons are taller than they are wide. Giant canyons often have a boxy or rectangular cross-section because they are significantly filled with sediments and breakdown - often more than 50% filled. At one site (at least), about 80 feet worth of fill is present.Shown above is Audubon Avenue, one of my favorite sections of Mammoth Cave. It is a relatively short stretch of impressive giant canyon passage. The dim lighting makes photography difficult. The view seen here is looking in the old downstream direction. A subterranean river used to flow through here. The ceiling is 30 to 40 feet above the level of the floor.Audubon Avenue is at level B in the Mammoth Cave system, which is the 2nd-oldest and the 2nd-elevationally highest set of passages. Level B passages started forming during the Pliocene, 2 to 4 million years ago.The ceiling and walls of Audubon Avenue consist of marine limestones of the Girkin Limestone (lower Upper Mississippian).Locality: Audubon Avenue (looking west from near the entrance to Little Bat Avenue), Mammoth Cave, Kentucky, USA |
| 撮影日 | 2013-01-20 12:02:42 |
| 撮影者 | James St. John |
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