听力原文
通过比较山顶与山脚的叶子化石，得出了一个惊人的结论。那就是在60万年前，落基山脉的高度应该是今天的两倍。为什么是这样的？那么大的山怎么会消失一半呢？Daisy很好奇，我要听下文啦！

After the Rockies emerged from the sea, it took them 10 million years to rise. Sixty million years ago, they reached spectacular heights of 28,000 feet, rivaling the Himalayas today. The deep history of the Rocky Mountains is beginning to take shape.

A weak line in the crust explains why the Rockies rose 500 to 1000 miles inland. Fossil leaves show that the young Rocky Mountains were once nearly twice their size. Half of the rock that formed them originally has vanished. Scientists are now trying to unravel the processes that cut them down to the size they are today.

One hundred million years ago, a vast inland sea covered the area where the American Rockies stand tall today. Seventy million years ago, the sea retreated as the Rockies began to rise. Sixty million years ago, the Rocky Mountains reached their pinnacle, towering into the sky with peaks over 28,000 feet high, rivaling the Himalayas.

Since then, the entire mountain range has lost nearly half its height. Geologists investigating the history of the Rockies are trying to discover what happened to the billions of tons of rock that went missing. The investigation starts with a mystery at the Owl Creek Mountains in the Wyoming Rockies. The Mountains are sliced by a river that has formed a deep canyon.

"Well, the Wind River is very perplexing. It chose to take a straight path right through the core of a major mountain range. This is not the way that rivers normally act. Usually it will take the easiest route which is a downhill. But this river cut right through a major mountain range and has been a mystery. It is a very perplexing issue to early geologists in the region."

This river led to confusion as early as 1806 when Marry Whether Louis and William Clark mapped the area during their famous expedition to explore uncharted territory.

小编有约：哦，本期的听力中有一个非常著名的“刘易斯与克拉克远征”，Daisy简单介绍介绍，刘易斯与克拉克远征（Lewis and Clark expedition，1804年–1806年）是美国国内首次横越大陆西抵太平洋沿岸的往返考察活动。领队为美国陆军的梅里韦瑟·刘易斯上尉（Meriwether Lewis）和威廉·克拉克少尉（William Clark），该活动是由杰斐逊总统所发起。大家应该猜到，由总统发起的，一定是想夺得这里的土地啦！呵呵~~具体详情就自己查啰。

课后题目：Daisy想让大家自己了解了解美国的地理，你能告诉我，文中出现的“ Owl Creek Mountains”在美国哪里吗？它有什么特征呢？

课后答案
呵呵~~答案就是" The investigation starts with a mystery at the Owl Creek Mountains in the Wyoming Rockies. The Mountains are sliced by a river that has formed a deep canyon. "它在文章的哪一段呢？找找看哦！Daisy也查了一些这里的图片，真的很漂亮。你也可以动手看看这里的图片。

参考译文
落基山脉用了10万年的时间从海中升上来。在6000万年前，洛基山脉就有28000英尺，这个壮观的高度可以与今天的喜马拉雅山脉有的一拼。同时落基山脉悠长的历史也开始了。

地壳中一个浅浅的痕迹解释说明了落基山脉为什么会上升到500至1000英里的内陆。那些叶子化石向我们证实，最初的洛基山脉，几乎是现在的两倍高。最初形成的岩石有一半已经消失了。科学家正试图解开落基山脉下降的谜团。

一亿年前，有一个巨大的内陆海，它的范围正好覆盖住整个美国落基山脉。70000万年前，海水退去，落基山脉开始上升。早在6000万年前的洛基山脉，已经达到自己的巅峰，超过28000英尺高的山峰，与喜马拉雅山脉不相高下。（注明喜马拉雅山最高峰 珠穆朗玛峰 29,017.16英尺）

从那以后，整个山脉慢慢地失去将近一半的高度。地质学家调查落基山脉的历史，试图发现究竟发生了什么事情使的数十亿吨的岩石，消失的无影无踪。调查从猫头鹰溪山开始，它位于怀俄明州的落基山脉，这儿也是充满了神秘。这片山被一条河削成片状，并形成了很深的峡谷。

“哦，这条风河是非常复杂的。它选择的路径正好穿过核心山脉的中心。一般情况下，河流是不会这样走的。通常的河流会走一条最简单的路线流到山下。但是这条河却穿过一条主要的山脉。因此它成为了一个谜，在该地区很早就有地质学家注意到这个令人困惑的问题。

早在1806年，梅里韦瑟•刘易斯和威廉•克拉克非常著名的探索之旅中，他们就来到过这里，当时在绘制该地区的地图时，这条河就曾让他们感到非常迷惑。

重点讲解
注释：① emerge vi. 浮现；摆脱；暴露
例句：
1. My sheep and cattle will emerge before your eyes.
风吹草低见牛羊。
2. Consensus did not emerge from a compromise between individual preferences.
意见一致并不是个人不同爱好的折衷产物。

② cut down v. 削减；砍倒；杀死；删节；胜过
例句：
1.The article is too long and should be cut down by half.
这篇稿子太长, 得砍去一半。
2. Do not cut down the tree that gives you shade.
[谚]遮荫之树不可砍。

③ cover vt. 包括；采访，报导；涉及 n. 封面，封皮；盖子；掩蔽物
vi. 覆盖；代替
词组：
from cover to cover 从头至尾
under cover 隐藏着；秘密地
cover up 掩盖，盖住
cover for 代替
cover with 覆盖
例句：
1. The front cover of the novel has been torn off.
这本小说的封面已被撕掉。
2. The pretty girl on the cover of the book is just a sales gimmick.
书封面上印上美女不过是吸引顾客的一种生意眼。
3. Snow covered the ground.
雪覆盖了大地。

句子讲解：

1. The deep history of the Rocky Mountains is beginning to take shape.

　　【结构简析】 Daisy认为这个句子，可以说明中西方的语言特点。“形合”和“意合”是已故语言学家王力先生所译。形合指句子内部的连接或句子间的连接采用句法手段（syntactic devices）或词汇手段（lexical devices）。意合指“句子内部的连接或句子间的连接采用语义手段（semantic connection）”（方梦之，2004）。印欧语言重形合，语句各成分的相互结合常用适当的连接词语或各种语言连接手段，以表示其结构关系。汉语重意合，句中各成分之间或句子之间的结合多依靠语义的贯通，少用连接语，所以句法结构形式短小精悍。像本句中的"is beginning to " 就是很好的例子，来说明落基山脉的历史从这里开始。

　　【参考译文】 同时落基山脉悠长的历史也开始了。

　　2. Sixty million years ago, the Rocky Mountains reached their pinnacle, towering into the sky with peaks over 28,000 feet high, rivaling the Himalayas.

　　【结构简析】这句话中，有两个现在分词" towering " 和 "rivaling"，做伴随状态来说明落基山脉的情况。

　　【参考译文】早在6000万年前的洛基山脉，已经达到自己的巅峰，超过28000英尺高的山峰，与喜马拉雅山脉不相高下。