[00:01.42]Could it be that drastic water shortage was the reason for the mastodons' epic migrations? 
会不会是因为极度缺水使得乳齿象进行了这么长距离的迁徙？
[00:17.08]Another big piece of this puzzle lies far out to sea. 
这个谜团的另一条线索位于海洋深处。
[00:34.49]This is the ocean floor. But this isn't rock sprouting out at the bottom. 
这就是大洋底。但是它的形成却不是因为底部地壳的挤压。
[00:51.19]It's wood. It's the remains of prehistoric tree stumps, some dated at more than 12,000 years old. 
这些都是木头，是史前时期树桩的化石，其中的一些可以追溯到12000多年前。
[01:10.01]This sunken forest is unmistakable evidence that what is now seabed was once dry ground. 
很明显，这些沉入海底的树林可以证明，这片大洋底所处的位置曾经是片干地。
[01:27.28]And what is now Florida's coastline was once many miles in land. 
现在佛罗里达的海岸线曾经都是数英里的陆地。但这又是为什么？
[01:33.91]But why? To answer that, we have to go back to the mighty ice age glaciers that covered almost half the continent. 
为了回答这一问题，我们需要回到冰河时代，看看覆盖了半片大陆的大冰期冰川。
[01:48.20]These glaciers contained immeasurable amounts of ice. 
这些冰川蕴含的冰的数量无法估量。
[02:10.91]So much water was locked up in this ice that it lowered sea levels by over 70 meters. 
这些冰川中贮存着大量的水，因此，那时的海平面比现在低70多米。
[02:18.21]The southeast coastal shelf was exposed and Florida doubled in size. The Everglades were dry land.  
东南部的沿海大陆架还处于地表之上，而佛罗里达的面积也是现在的两倍大。那时的大沼泽地还是一片干燥的陆地。