听力原文
上次咱们在怀俄明州的盆地发现了什么呢？它能否告诉我们落基山下降的原因呢！咱们接着听！

Rock and cobbles eroded down from the Bighorn Maintains and filled up the basin to at least a thousand feet, the height of the Pumpkin Buttes.

"Pumpkin Buttes are unique because this used to be the actual surface level of the basin itself. The rest has been eroded away a thousand feet of sediment to the basin that we see now."

But the rubble found here is nowhere near enough to have covered the Owl Creek Mountains. Mclaughlin traveled to Darton's Peak, one hundred miles west in the Bighorn Mountains. On a cliff, 9000 feet high, he finds granitic cobbles that are strikingly similar to the ones on the Pumpkin Buttes. They too, are from the core of the Rocky Mountains.

"The core of the Rocky Mountains are made extensively of granite. Much like what you see here, these are from the Bighorns that have been transported down, rolled and smoothed along their way to create these smaller boulders and cobbles."

This is strong evidence that cobbles eroding from the Rockies filled in the basins and valleys to at least 9,000 feet, slowly burying the Mountains under their own debris. Where once the mighty Rockies stood, there was now a grey barren plain with only the peaks of the old Mountains piercing the surface.

The same process has happened in other mountain chains too. There was evidence that the European Alps were also cut in half by erosion. At their base, scientists found hills formed out of millions of tons of rock that had cascaded down and reduced their height. But the story of the eroding Rockies wasn't over yet. After erosion turned the landscape into a great cobble field, another disruption happened. Evidence for this is a layer covering the top of the cobbles.

"It’s very light, it's very fine-grained. It's actually of volcanic ash. As you can see, it's made of very very fine-grained sediments compared to this boulder conglomerate, just made of big hunks of rock. It sits directly on top of this unit and it was laid horizontally from mostly ash-fall."

小编有约：这期终于给咱们解开了这个谜团，为什么洛基山脉会下降，你有了答案吗？能告诉Daisy吗？

听力答案
呵呵~~答案就是"This is strong evidence that cobbles eroding from the Rockies filled in the basins and valleys to at least 9,000 feet, slowly burying the Mountains under their own debris. " 。看看他们在哪一段呢？

参考译文
从大角山侵蚀下来的岩石和卵石填补了低洼的盆地至少一千英尺，也就是今天南瓜巴茨山们的高度。

“南瓜巴茨山是独一无二的，因为这里曾经是盆地的水平面，其余剩下的已被侵蚀成一千英尺的黄沙盆地，就像我们现在看到的这样。”

但是在这儿发现的碎石，不是覆盖猫头鹰山脉的碎石。麦克劳克林前往达顿的山顶，位于大角山以西一百英里。在悬崖上，9000英尺高的地，他发现这里的花岗岩石与南瓜巴茨山上的鹅卵花岗岩石是惊人地相似。这些花岗岩石来自落基山脉。

“落基山脉主要是由花岗岩组成。就像你在这里看到的一样，这些从大角山上松动，滚下山的石头，沿着自己的轨迹，一路上磕磕碰碰成为了小石块和平滑的鹅卵石 。”

这个强有力的证据表明从落基山脉上腐蚀掉下来的卵石填充了盆地和山谷至少9000英尺，慢慢地落基山脉便被自己的小碎石所填充。曾经在这儿不可一世的落基山脉，现在只留下那灰色贫瘠的平原，和破土而出的山峰。

这样的经历同样也会发生在其他山脉。有证据表明，欧洲的阿尔卑斯山同样也被侵蚀了一半。在他们的底部，科学家发现了一串串的岩石成阶梯状的排下来所形成的小山，逐步减少他们的高度。洛基山脉的侵蚀故事还没结束。这里的岩石侵蚀成许多的小卵石后，另一个灭顶之灾随之到来。证据就是有一层物质覆盖在卵石的上面。

“它很轻，很细。实际上就是火山灰。正如你看到的那样，与成团的大石块相比，它是非常非常细的沉积物，这些石块团是由大岩石组成。火山灰直接落在这些大岩石的上面。而这些岩石能够水平放置，还得多亏了这些火山灰。”

重点讲解
注释：① at least 至少
例句：
1. She may be slow but at least she's reliable.
她迟钝是迟钝，但无论如何她很可靠。
2. We should brush our teeth at least twice a day.
我们每天应该至少刷两次牙。

② rubble n. 碎石，碎砖；粗石堆
例句：
1. Many people were entombed in the rubble of the bombed buildings.
很多人被埋在炸毁的建筑物的瓦砾里。
2. The ceiling collapsed and rubble poured into the room.
天花板坍塌了，碎砖破瓦掉落到了屋里。

③ compare to 把......比作，比喻为
例句：
1. Compare to his early work, this be a rather slight novel.
这部小说与他早期作品相比, 不甚重要。
2. Can you tell me how this compare to that ?
你能告诉我这个和那个比较起来如何？

句子讲解：

1. Rock and cobbles eroded down from the Bighorn Maintains and filled up the basin to at least a thousand feet, the height of the Pumpkin Buttes.

　　【结构简析】 这里是由"and"连接的两个动作，一个是"eroded down",然后是"filled up"，后面的是一个定语补充说明一千英尺的。

　　【参考译文】 从大角山侵蚀下来的岩石和卵石填补了低洼的盆地至少一千英尺，也就是今天南瓜巴茨山们的高度。

　　2. But the rubble found here is nowhere near enough to have covered the Owl Creek Mountains.

　　【结构简析】这里有"nowhere" 这个单词，就是按照它本来的意思理解。不受到后面的"near enough to" 的影响。

　　【参考译文】但是在这儿发现的碎石，不是覆盖猫头鹰山脉的碎石。