Explorers have tracked one formation for 4 miles - so far

by Susan Montoya Bryan, Associated Press

Fort Stanton Cave, N.M. --

Hundreds of feet beneath Earth's surface, a small group of seasoned cave explorers venture where no human ever has set foot. With each careful step they take, their headlamps illuminate walls covered with mud, gypsum crystals and mineral deposits left behind by microscopic organisms eating through fractured rocks.

The real attraction, though, is under their shoes.

A quick pass of a headlamp over the cave floor reveals a massive formation that resembles a white river flowing between the cave's banks. As the light shines more intensely on the odd and seemingly endless formation, an intricate crust of tiny calcite crystals comes into focus.

They've reached Snowy River - already the longest-known continuous cave formation in the world, with no end to it yet in sight.

"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," says Jim Goodbar, the senior cave and karst specialist for the Bureau of Land Management.

The survey expedition by members of the Fort Stanton Cave Study Project in early July added several thousand feet of known terrain to the spectacular formation, which now measures 4 miles long.

The best part, the cavers say, is that the passage they've been following under the rolling hills of southeastern New Mexico is getting larger and the air flow is strong, suggesting there's still more of Snowy River to be discovered.

The select few who have walked on the formation say there appears to be nothing else like it. Early studies of Snowy River also point to its uniqueness: Already, some three dozen species of microbes previously unknown to science have been uncovered.