A blue hole in the Bahamas
STEVE EMBER: These flooded cave systems can be found in the ocean, or they can be found inland. Ocean caves are affected by tides, so they always have water movement. But blue holes on land are very still. They have several layers of water, chemicals, and bacteria. The top layer of fresh water comes from rainfall. This layer acts like a cap on top of the layered mixture, and keeps out oxygen from the atmosphere. The fresh water floats on a denser layer of saltwater. Underneath this is a layer of poisonous hydrogen sulfide, produced by bacteria living in the water. Underneath this layer is anoxic seawater -- water that does not contain any oxygen.
BARBARA KLEIN: Kenny Broad is an anthropologist at the University of Miami in Florida. He studies the effects of climate change and human understanding of its risks. He has spent several years exploring underwater caves in the Bahamas. Here Mr. Broad discusses his many cave explorations during a talk at the National Geographic Society in Washington, D.C.
KENNY BROAD: “Underwater caves are probably, I would argue, one of the least understood ecosystems on the planet. One of the reasons they are one of the least understood, they are one of the least explored. And they are one of the last places where you still physically have to go there, you can’t send in a submarine or a mode operated vehicle, some autonomous machine. You need to go there.”
最新
2013-11-25
2013-11-25
2013-11-25
2013-11-25
2013-11-25
2013-11-25