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来到了落基山国家公园 ，看到了最高峰是久久峰(Longs Peak)，它高达14255尺。这里大多数是陡峭的悬崖和锯齿状的峭壁，究竟是什么原因呢？值得探索！
Back on the ground, Anderson is looking for evidence that will reveal the processes that shaped the jagged peaks. On a hillside, he finds mysterious large boulders scattered across the valley floor. A closer look uncovers some secrets about their origin.
"I'm standing in front of a rounded boulder that itself is sitting on a smooth, bedrock （基岩）outcrop（露出地面的岩层）. Both the boulder and the outcrop are covered in lichen （地衣，苔藓）here of green to black to grey colours. And therefore I had to whack up a piece of the rock in order to see inside the rock. And indeed it is different. The mineral(s) that I see in the texture of the rock is different from the underlying rock. And therefore the rock is (a) foreign to this particular site."
Anderson searches the ground for more clues as to how this massive boulder got here. Nearby he finds a smooth surface with very fine scratch marks.
"I'm sitting on a polished surface. This little piece right here is smooth to the touch. And if I look at it in a certain way the light glints （闪闪发光）off, but just right I can see that there are scratches running in this direction across the surface."
The only force that could have produced this fine parallel scratches on the rock is ice, and lots of it. It's a clue that a massive glacier once filled this valley.
"And that tells me that the glacier came down the valley, came across this surface and eroded it. Each one of these scratches corresponds to a sand grain embedded in the sole of the ice, that just like sandpaper smoothes off the surface. So zillions of sand grains over thousands of years will have eroded this surface smooth."
As glaciers flowed down the valley, they picked up rocks and grit. The ice pushed down on these cutting tools with the weight of over a thousand fully loaded garbage trucks. It left scratch marks all over the Rockies up to a thousand feet high. This is evidence that a massive wall of ice covered this part of the Rockies and shaped the Mountains. The ice ripped out the rock from the valley walls and left behind the jagged cliffs and rugged edges.
小编有约：注意细节的人很容易成功，在这里作者就偶然发现圆滑的石头上面有小小的划痕，进而通过划痕发现冰川，通过冰川发现冰里面的沙子，通过沙子发现类似砂纸的功效。从而推断出为什么这里是陡峭的悬崖和锯齿状的峭壁。本文为小编自己翻译以及讲解的文章，如有改进的地方请大家留言！如有转载请注明来源！
课后题目：Daisy很想建议大家爬爬山，感受大自然的魅力，想一想自己家乡的山中会发生怎样的故事让人难忘呢？
