Jewel Cave, located in Jewel Cave National Monument, is officially the second-longest mapped cave in the world (behind Mammoth Caverns in Kentucky) with a length of 157 miles. Because of the length, it takes explorers a significant amount of time to reach the unexplored portions of the cavern, oftentimes requiring camping underground on expeditions of 4 or more days in length. According to Wikipedia, "The discovered areas in the cave account for only about 2% of the estimated total air volume of the cave. The cave volume is estimated by measuring the amount of air that the cave "exhales" when the outside air pressure drops and "inhales" when the outside air pressure rises."
Jewel Cave contains all of the traditional speleothems, although not in as high of quantities as some other well-known caverns. Some of the unique formations include a hydromagnesite balloon, which is formed by a gas inflating this substance.
The cave is open for tours all year long. There are 3 different tours offered, varying in difficult from very easy, short tours to spelunking tours through undeveloped caverns.
Posted by Greg Heil on March 23, 2012
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