Техас штатының Сонора үңгірі

Cave in Texas, United States

The Caverns of Sonora, a National Natural Landmark, is a unique cave located 8 mile (13 km) west of the small city of Sonora, the seat of Sutton County, Texas. It is a world class cave because of its stunning array of calcite crystal formations, especially helictites. These helictites are found in extreme abundance, often with a rare purity and complexity. One formation is so densely packed with them, it has been dubbed the "snake pit". The founder of the National Speleological Society, Bill Stephenson, said of the cave after his first visit: "This is the most indescribably beautiful cave in the world, its beauty cannot be exaggerated, not even by a Texan."

The cave is formed in 100 million year old (Cretaceous) Segovia Limestone, of the Edwards Group. The formation of the cave itself probably occurred between 1.5 and 5 million years ago. The cave is formed primarily along joints, which allowed gases to rise up from depths of around 1.5 mile (2 km) to then depths of about 300 feet (91 m). At this depth, the gases mixed with water in the aquifer. The resulting highly acidic water dissolved out the limestone, forming the cave. Between 1 and 3 million years ago, the water drained from the cave. The famous mineral formations, known as speleothems, all formed after the water drained from the cave. The cave's most famous formation was the butterfly. It was the only known formation like it in the world. It was formed by two fishtail helictite growths that share the same attachment point of the cave wall. In November, 2006, about a third of the right wing was broken off of the formation.

The first quarter mile of the cave was known to local ranch hands by the early 1900s. It was known by the name Mayfield Cave, after the landowner, Stanley Mayfield. In 1955, Stanley gave permission to four cavers from Dallas, who discovered a further seven miles, including what are now considered the most scenic areas.