Caverns of Sonora

The Caverns of Sonora, a National Natural Landmark, is a unique cave located 8 miles 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 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 a fault, which allowed gases to rise up from depths of around 1.5 mi to then depths of about 300 ft . 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.

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