注釋：① channel vt. 引導，開導；形成河道 n. 通道；頻道；海峽
[ 過去式channeled或-nelled 過去分詞channeled或-nelled 現在分詞channeling或-nelling ]
詞組：
marketing channel 銷售渠道，行銷通道
main channel 主通道
change the channel [美國俚語]轉移話題
english channel （英法之間）英吉利海峽
distribution channel 分銷渠道；銷售渠道
communication channel 通信信道；通信電路
river channel 河道；河槽；船舶航道
例句：
1. Mr Obama's speech was broadcast live by only one cable TV channel with limited reach.
奧巴馬的演講只通過一家有線電視頻道在有限的范圍內現場直播。
2. But after his landslide 10 years earlier he could have crossed the English Channel on foot.
但在10年前以壓倒多數勝選上臺后，他本可以“信步”跨越英吉利海峽。

② presence n. 存在；出席；參加；風度；儀態
詞組：
in the presence of 在…面前；有某人在場
in presence of 提示
physical presence 實體存在；實際存在
military presence 軍事存在
internet presence 網上廣告
commercial presence 商業存在
例句：
1. I mean by that , your presence will become meaningless .
我的意思是，你的存在會變得沒有意義。
2. For these the presence of people is central to the experiment.
由此說來，人類的存在正是這項實驗的核心。

③ impressive adj. 感人的；令人欽佩的；給人以深刻印象的
[ 比較級more impressive 最高級most impressive ]
例句：
1. At first glance, all this has produced some impressive results.
初看之下，這些措施都產生了明顯的效果。
2. This is the most impressive architecture I've seen on this trip.
這是我此次旅行見到的最令人難忘的建筑。

句子講解：

1. And every time they come across the landscape, they are capable of eroding that landscape at rates that are perhaps fractions of an inch per year, meaning that over the course of one glacial cycle, you perhaps erode ten, twenty feet of rock.

　　【結構簡析】整個句子是冰川每年侵蝕大約一英寸土地來做解釋說明的。主句為"they are capable of eroding that landscape at rates"。

【參考譯文】只要這些融化了的雪水到過的地方，每年就會侵蝕大約一英寸地，這就意味著，在一個漫長的冰期旋回過程中，可以侵蝕掉巖石十到二十英尺深。

　　2. They hitchhiked at the bottom of the glacier down the frozen valley, when the last Ice Age came to an end and the glaciers melted about 10,000 years ago, the boulders were left behind.

【結構簡析】 我覺得這個"hitchhike"這個詞用的非常好，這些石頭就像搭便車的人一樣，這個比喻迅速就讓人明白是怎么一回事啦。很形象。

　　【參考譯文】當最后一個冰河世紀結束的時候，巨石搭乘冰川的順風車來到了結冰的峽谷，冰川早在一萬年前融化，巨石則留在了這里。