英语听力：探索发现 2012-12-16 冰河新新州 Ice Age Oasis—2（在线收听） |
By piecing together the evidence these creatures left behind, we can build a picture of this sub-tropical corner of the continent as it was 13,000 years ago. While most of North America was still in the grip of the Big Freeze, Florida was an ice age oasis. Florida is aptly named the Sunshine State. With an average of eight hours of sun a day, it seems a world away from any ice age. Even 13,000 years ago, the massive ice sheets were hundreds of miles away to the north. So what was it like back then? To investigate Florida's ice age past, one of the best places to look is under ground and up the water. Just below the surface lies a very strange world. Millions of years of water action has dissolved the limestone rock, forming a system of flooded caves and tunnels. This vast underground network runs for thousands of miles. Much of Florida is basically a big rock honeycomb. In places the water is forced to the surface, forming springs. Florida has one of the largest concentrations of springs in the world. Filtered through sand and rock, the water is crystal-clear. And welling up from deep within the earth, it is a constant 22 degrees centigrade. |
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