Breakdown in a giant canyon passage (Edwards Avenue, Great Onyx Cave, Flint Ridge, Mammoth Cave National Park, Kentucky, USA) : 無料・フリー素材/写真
Breakdown in a giant canyon passage (Edwards Avenue, Great Onyx Cave, Flint Ridge, Mammoth Cave National Park, Kentucky, USA) / 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 | Breakdown in a giant canyon passage in Great Onyx Cave.Great Onyx Cave is located in the northern part of Flint Ridge in Mammoth Cave National Park, Kentucky, USA. It has 8 miles worth of mapped passages. Geologically, Great Onyx Cave is part of the Mammoth Cave System, but it has become erosively separated from it (although an air flow connection with the Mammoth Cave System has been identified). Great Onyx Cave is the downstream continuation of the Salt Cave section of the system.The walls of Great Onyx Cave are limestones of the Paoli Member, shales of the Bethel Member, and limestones of the Beaver Bend Member of the Girkin Formation (lower Upper Mississippian). The travertine speleothem-rich areas of Great Onyx Cave are wet and occur where a cap of overlying Big Clifty Sandstone is absent. The dry portions of the cave are below an intact Big Clifty Sandstone "caprock", and include the giant canyon passage areas and the gypsum speleothem areas.The main cave passage of Great Onyx Cave is called Edwards Avenue (see above photo), developed at Level B in the Mammoth Cave System. Level B passages formed about 2 to 4 million years ago during the Pliocene. Edwards Avenue is a giant canyon passage. Canyon passages are tall and narrow, and form in the vadose zone (above the water table). Giant canyon passages (a.k.a. rectangular passages) are much larger and can form in either the vadose or phreatic zone (at or below the water table). They are usually more than half-way filled with sediments and breakdown (see above photo). Breakdown refers to large limestone blocks on cave floors that have detached from ceilings or walls. Breakdown piles can fill entire cave passages, which blocks further exploration. Breakdown piles often occur below surface sinkholes (Ex: Lookout Mountain in Rafinesque Hall next to Audubon Avenue, along an active tourist trail in Mammoth Cave Ridge).This cave is sometimes accessible to the general public by guided lantern tours during boreal summer months. This photo was taken during a field trip in June 2011 as part of a cave geology course at Mammoth Cave park. |
| 撮影日 | 2011-06-16 14:41:24 |
| 撮影者 | James St. John |
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