托福听力短文 II-09-1

(MA) Look at our topographical map and you'll see that the middle third of the North American continent --- from the Rocky Mountains almost to the Mississippi River --- is pretty flat. This is the Great Plains. This kind of area is sometimes called a prairie, sometimes a steppe. That's [ess-tee-ee-pee-pee- ee]. The defining features are level terrain¹, dry climate, and an absence of trees. The Great Plains are actually the former bed of shallow inland sea. Over millions of years, sediment² left by glaciers³, water, and wind smoothed out the dry sea bed.

As I said, the Great Plaints are bordered on the west by the Rocky Mountains. And it's really the Rockies that are responsible for the formation of the grasslands⁴. The mountains are so high that they block the heavy moist air traveling eastward⁵ form the Pacific Ocean. Lighter⁶, drier air passes over the mountains. Until people intervened with irrigation and farms, only grass could grow on the dry, windy plain. In fact, we can divide the Great Plains into three zones. In the west, where it's driest and windiest, the grass is very short. In the eastern zone, there's more rain and grass grows as high as 360 centimeters. In the middle third, there's a mix of grass species that grow to an intermediate height.

1 terrain   

n.地面，地形，地图

参考例句：

• He had made a detailed study of the terrain.他对地形作了缜密的研究。
• He knows the terrain of this locality like the back of his hand.他对这一带的地形了如指掌。

2 sediment   

n.沉淀，沉渣，沉积(物)

参考例句：

• The sediment settled and the water was clear.杂质沉淀后，水变清了。
• Sediment begins to choke the channel's opening.沉积物开始淤塞河道口。

3 glaciers   

冰河，冰川( glacier的名词复数 )

参考例句：

• Glaciers gouged out valleys from the hills. 冰川把丘陵地带冲出一条条山谷。
• It has ice and snow glaciers, rainforests and beautiful mountains. 既有冰川，又有雨林和秀丽的山峰。 来自英语晨读30分（高一）

4 grasslands   

n.草原，牧场( grassland的名词复数 )

参考例句：

• Songs were heard ringing loud and clear over the grasslands. 草原上扬起清亮激越的歌声。 来自《现代汉英综合大词典》
• Grasslands have been broken and planted to wheat. 草原已经开垦出来，种上了小麦。 来自《简明英汉词典》

5 eastward   

adv.向东；adj.向东的；n.东方，东部

参考例句：

• The river here tends eastward.这条河从这里向东流。
• The crowd is heading eastward,believing that they can find gold there.人群正在向东移去，他们认为在那里可以找到黄金。

6 lighter   

n.打火机，点火器；驳船；v.用驳船运送；light的比较级

参考例句：

• The portrait was touched up so as to make it lighter.这张画经过润色，色调明朗了一些。
• The lighter works off the car battery.引燃器利用汽车蓄电池打火。