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云龙地缝的形成
“地缝”（Difeng）现在已经是地学界接受的一个“喀斯特地貌”术语，它是指非常狭窄且有相当深度与长度的峡谷或流水沟谷，形态上表现为地壳表面的一条深切“天然岩缝”。由于其形成、保存十分困难，“地缝”也就成了旅游的热门景点。一般的地缝是下面窄，上面宽，有的是上面窄，下面宽，而像云龙河地缝上下垂直基本一致断面呈“U”字形的地缝极为罕见，目前世界上只发现罗马尼亚有类似的地缝，所以它的稀缺性、独特性可见一斑。
据考察，云龙地缝自谷底向上至谷坡、谷顶，主要出露二叠纪（2.5-2.95亿年）和三叠纪（2.03-2.5亿年）碳酸盐岩。地缝的形成最早始于喜马拉雅运动（大约3千万2百万年前），由于地壳运动使得鄂西山地抬升，区域地层发生变形并伴生剪切破裂，产生了大量的陡倾或直立的X型共轭节理裂隙，随着变形作用加强就形成了追踪张开裂隙，并不断被加深拓宽。后期的风化、冲蚀、坍塌等外力地质作用使得追踪张开裂隙处于谷底地带，成为早期的云龙河伏流段，且以暗河形式沉睡地下二、三千万年，后因水流在地下强烈掏蚀，在地表不断剥蚀，致使暗河顶部坍塌，地缝才得于面世，构成恩施大峡谷一大奇观。
THE FORMATION OF THE YUNLONG GEO-FRACTURE
Geo-fracture, known as Difeng in Chinese, is now a terminology of a karst landform adopted by the geological circle. It refers to a narrow gorge or fissure with flowing water that has a considerable depth and length, which is formally a “natural fissure” deeply cut in the earth’s crust. Thanks to the great difficulty in its formation and conservation, it is a rarity in the karst landforms and also a favorite tourist haunt. Usually, a geo-fracture is narrow at the bottom and wide at the rim, or the other way round but such geo-fracture as the Yunlong Geo-fracture with nearly vertical precipices and a U-shaped section is rarely seen so it is rare and the most peculiar of all geo-fractures ever known.
Research has revealed that in the Yunlong Geo-fracture, from the bottom to the waist of the precipice and the rim, the exposed rocks are mainly carbonate rocks of the Permian Period (295-250 million years ago) and the Triassic Period (250-203million years ago). The formation of the geo-fracture started as early as in the Himalayan Orogeny （some 32 million years ago）. As the crustal movement raised what is the mountainous region in western Hubei Province, the local stratum was deformed, cut and faulted, resulting in a large number of steeply inclined or vertical X-shaped conjugate joint fissures. With the increase of the deformation the joint fissures turned into tracking open fissures, which were further deepened and widened. Subsequent external forces such as weathering, erosions and carving-in followed the tracking open fissures to the valley bottom, forming the underground part of the Yunlong River in its early years and it had remained in that form for 20-30 million years. Later on, both the powerful rinse by the underground water current and the incessant erosion of the earth’s surface caused the collapse of the vault of the underground river, the geo-fracture finally came into being and became one of the highlights of the wonderful Enshi Grand Canyon.