The opening in the craggy rock face is no bigger than a guitar case, yet caver Steve Lewis, even at 6 feet tall, seems unfazed, and quickly drops his long body underground to meet Kevin Allred and Pete Smith, his two somewhat shorter fellow explorers. There, 10 feet beneath giant Sitka spruce and the fierce winds of Prince of Wales Island, Alaska, a dry, narrow passage opens into what may as well be a different planet. The glow from their carbide lights illuminates scalloped walls of a meringue-like crystalline mineral that drips into delicate stalactites. The air is cold, silent and still; it's easy to imagine this is some ancient tomb.
"This is our last frontier. The deep sea and these caves up here are the only unexplored places left," says the 48-year-old Smith, his sinewy form crouched beneath the cave's slanted roof. "You can climb a cliff that no one's been on before, but at least you can see where you're going. When you enter a cave, you don't know what you're going to find. The smallest passage could lead to a 500-foot room."
Created hundreds of thousands of years ago by rainwater that eroded porous limestone bedrock, caves such as this one, underground rivers and deep pits speckle the 16.9 million-acre Tongass National Forest of southeast Alaska. During the last 13 years, Lewis, Allred and Smith, along with others with whom they work, have discovered nearly two-thirds of the 600 known caves in the area. They estimate there could be 600 more, making this one of the best cave landscapes--known as "karst"--in the world. Unaffected by development, these caves have revealed 41,600-year-old bear bones, 10,000-year-old human bones and the skeletal remains of thousands of birds, mammals and fish from before, during and after the Ice Age. Such findings have led paleontologists and archeologists to reconsider theories of human migration into North America.