Mudcracked sediments (River Hall, Mammoth Cave, Kentucky, USA) 4 : 無料・フリー素材/写真
Mudcracked sediments (River Hall, Mammoth Cave, Kentucky, USA) 4 / 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 | Modern mudcracks in a cave in Kentucky, USA. (March 2024)Mudcracks are diagnostic sedimentary structures indicating subaerial exposure of sediment surfaces, with alternating wet & dry conditions. They are much more common that raindrop imprints, which indicate the same environmental setting. Mudcracks are most likely to occur in fine-grained siliciclastic sediments, fine-grained carbonate sediments, and in some evaporitic settings. Mudcracks are distinctive and easy to identify, but they do vary in appearance. The cracks themselves vary in width, depth, and areal density. Mudcrack polygons also vary in size & shape.The mudcracks seen here are developed in a relatively thin mud layer overlying sand in a cave passage at Mammoth Cave, Kentucky. The cave is a complex network of passages in Mississippian-aged limestones. The lowest levels are at and below the modern water table. Water flows from the deepest passages toward the Green River. During and after storms, the Green River experiences high flow, which results in water levels rising in the cave. The site here has been inundated many times, resulting in deposition of sands and muds. After flood events wane, the water table lowers and the area becomes subaerially exposed again. Then, the capping mud layer dries out and cracks. In some examples, the edges of the mudcrack polygons curl upward.Locality: trailside in the Dead Sea area, River Hall, Mammoth Cave, near the northwestern end of Mammoth Cave Ridge, Edmonson County, western Kentucky, USA----------------------------------------------(accessed with park permission) |
| 撮影日 | 2024-03-12 15:41:01 |
| 撮影者 | James St. John |
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