South Dakota’s Jewel Cave Nearing 175 Miles Long

January 13, 2015 / South Dakota, United States, North America

Inside South Dakota’s Jewel Cave. Photo via NPS

Cavers recently extended the known length of South Dakota’s Jewel Cave to 173.89 miles (279.849 kilometers) long.

Jewel Cave National Monument reports that cavers on recent trips gained the length by conducting ‘mop up’ surveys, probing leads along the main surveyed route.

The next survey trip is planned for February and, with no end in sight, it is expected that cavers will then push Jewel Cave past the 175th mile.

Jewel Cave is currently the third longest known cave in the world behind Kentucky’s 400 mile (643.7 kilometer) long Mammoth Cave System and Sistema Sac Actun in Mexico’s Yucatán Peninsula, at 206.9 miles (332.9 kilometers).