Fort Stanton Cave, New Mexico:

Hundreds of feet beneath Earth’s surface, a few seasoned cave explorers venture where no human has set foot. Their headlamps illuminate mud-covered walls, gypsum crystals and mineral deposits.

The real attraction, though, is under their shoes.

A massive formation that resembles a white river spans the cave’s floor. A closer examination reveals that the odd formation is an intricate crust of tiny calcite crystals.

The explorers have reached Snowy River — thought to be the longest continuous cave formation in the world.

”I think Snowy River is one of the primo places underground in the world and there’s still so much left that we haven’t discovered. … We don’t even know how big it is,” said Jim Goodbar, a cave specialist with the federal Bureau of Land Management.

The survey expedition by members of the Fort Stanton Cave Study Project in early July added several thousand feet to the measurement of the spectacular formation, which is at least four miles long. The explorers who have been following the passage under the rolling hills of southeastern New Mexico say there’s still more of Snowy River to be discovered.

The few who have walked on the formation say they’ve seen nothing else like it. Early studies point to its uniqueness: Already, some three dozen species of microbes previously unknown to science have been uncovered…

Last summer, explorers were surprised to arrive at Snowy River and find it flowing with water. It had been dry when first discovered in 2001 and during trips in 2003 and 2005.

It took several months for Snowy River to dry out, leaving scientists with another set of questions about where the water came from and where it went. Some scientists believe innumerable floods formed Snowy River, dropping a thin layer of calcite each time.

Areas of Fort Stanton Cave are open to those who get permits from the BLM, but Snowy River — deep in the cave behind locked metal gates — is off-limits. It’s unlikely Snowy River ever will be open to anything but research because of the fragility of the tiny calcite crystals and microbes on the cave walls.

New York Times