National Geographic : 2010 Aug
EDITOR'S NOTE Wes Skiles took this photo of veteran diver Kenny Broad as they began their descent into the hydrogen sulfide zone of a Bahamas blue hole. PHOTO: WES C. SKILES Photographer Wes Skiles descends through 30 feet of fresh water and encounters a pink, murky haze. The color indicates the presence of hydrogen sulfide gas---produced by decaying organic material in environments where oxygen is scarce---and it's dangerous. Skiles has little time to traverse this 20-foot-thick, toxic layer. The longer he lingers in this sulfurous hell, the more the risk. His head will begin to throb. He'll get a tingling sensation in his lips. He'll feel nauseous from oxygen deprivation. He must reach the saltwater layer below before he collapses. Skiles, writer Andrew Todhunter, and a team led by Kenny Broad, an anthropologist and veteran cave diver, are on a National Geographic--funded expedition to explore the flooded limestone caves of the Bahamas. These blue holes, the subject of this month's cover story, are an environment like no other. Their dangers are also like no other. Many caves produce violent whirlpools that can rip off a face mask and suddenly suck a diver down hundreds of feet. The risk is worth it. To study blue holes is to deepen our understanding of the Earth's biology, chemistry, and geology. Some of the caves, Todhunter writes, are the scientific equivalent of Tut's tomb. "It's true exploration, " Skiles says. Explorers, like Broad's team of scientists and divers, open doors. They lift the curtain on hidden, some- times dangerous, worlds. That's their nature, and our world is richer for it.