英语听力：探索发现 2012-11-09 美洲大平原 American Serengeti—6

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Scavengers would have been attracted by the mammoths' plight³. The bones of wolf, coyote, and the short-faced bear have also been recovered from the dried-up sediment⁴. The search for food was probably their death pool,too.

 

These prairie ponds are like time capsules. And they store another kind of data, showing how the plains have changed across millennia⁵. Each spring, pollen⁶ from nearby plants is blown into the water. It sinks and settles layer upon layer on the bottom, building into a data bank of local plant life that we can still read today.

 

And grass pollens⁷ aren’t the only clue still sandwiched in the sediment. There are a wide variety of tree pollens, too, from aspens, spruce and other trees, both coniferous and deciduous⁸.

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