National Geographic : 2011 Jan
• Doong," Howard says. "Khanh had found the entrance as a boy but had forgotten where it was. He only found it again last year." Stands of bamboo and other vegetation cover mounds of limestone here, making the place all but impenetrable. Below the surface, this part of Vietnam is one immense limestone block, says Darryl Granger, a geomorphologist from Pur- due University. " e whole region was squeezed upward when the Indian subcontinent smashed into the Eurasian continent 40 to 50 million years ago," he says. Hang Son Doong was formed two to ve million years ago, when river water owing across the limestone burrowed down along a fault, scouring out a giant tunnel beneath the mountains. In places where the limestone was weak, the ceiling collapsed into sinkholes, creating the gigantic skylights. Anette Becher, a German caver and biologist, has found wood lice, sh, and millipedes inside the cave that are all white, which is common for creatures that live in the dark. And Dai Inh Vu, a botanist from the Vietnam Academy of Science and Technology, has identified the plants growing beneath the skylights, nding basically the same mix that grows in the forest above. But such science on the run is not the real focus of this expedition, whose central pur- pose is exploration. For cavers like the Limberts, discovering a cave as big as Hang Son Doong is like finding a previously unknown Mount Everest underground. "We've just scratched the surface here," Howard says of the national park, which was named a World Heritage site in 2003 for its forests and caves. " ere is so much more to do." When Howard and Deb rst saw these enor- mous spaces, they felt certain they had discovered Hang Son Doong's airy chambers sprout life where light enters from above---a different world from the bare, cramped, pitch-black spaces familiar to most cavers. Ferns and other greenery colonize rimstone (above). In the jungles directly beneath roof openings, explorers have seen monkeys, snakes, and birds.