新托福阅读：Ice Quake

冰原地区的冰震。

Over a hundred quakes have happened in the last decade. But they didn't occur near fault lines(断层线). What were they near? Find out on this Moment of Science.

We’re used to thinking of earthquakes as (1)tremors(震动，颤抖) that happen along fault lines when tectonic plates ((地球表面的)构造板块)shift. They’re dramatic(吸引人注目的) events: a good-sized(相当大的，大型的) earthquake can bring buildings and bridges (2)toppling down(推翻;倒塌).

Those destructive energy bursts are high frequency(高频) ground vibrations(震动), and that’s the range of vibrations seismologists(地震学家) most actively study. Just recently, though, a geophysicist(地球物理学者) at Harvard University named Göran Ekström studied low-frequency(低频的) vibrations instead, and discovered something interesting.

He found over a hundred quakes have happened in the last decade that aren’t along any fault line. What are they near instead? Ice.

A glacier(冰川) can be thought of as a very (3)slow-moving(动作缓慢的) stream. It’s made of solid ice, but over long periods of time it can flow gradually over the land, sometimes carving deep (4)trenches(沟，沟渠) and (5)bulldozing(推土) up rock and soil. Just because it takes centuries to rearrange(重新排列) things, though, doesn’t mean a glacier isn’t enormously powerful at any given moment.

By carefully measuring seismic(地震的) signals, Ekström was able to spot numerous low-frequency quakes in Greenland that hadn’t been identified. He also found that they mostly occurred during July, August, and September. Those warmer months melt lots of glacial ice.

Ekström suspects that liquid water is (6)pooling(淤积) underneath the glacial ice to the point where the thin (7)veneer(外表) of water at the base of the glacier allows the whole mass to slip(滑动) a little, the way your foot can skid(打滑) on a slick(光滑的) road.

The quakes he recorded, he believes, are the vibrations set up by all that ice–in one case, six cubic(立方的) miles of it–skidding as much as forty-two feet in under a minute. When that much ice scrapes(刮掉，擦掉), the earth itself shakes.

Notes:

(1)tremors ['treməz] n.震动;颤抖(tremor的复数)v.颤动(tremor的三单形式)

1.They got only blushes, ejaculations, tremors, and titters, in return for their importunity.

她们只是用脸红、惊叫、颤抖和傻笑来回答他们的要求。

2.Rescuers are continuing into a third day the hunt for survivors of the earthquake that hit Peru's central coast, as fresh tremors shake the area.

救援一直持续到了第三天，搜寻发生在秘鲁中部海岸的地震后的幸存者，这次地震又引起了这个地区的震动。

(2)topple down 推翻;倒塌

The wounded soldier toppled down time after time.

伤兵一次又一次地跌倒。

(3)slow-moving ['sləu'mu:viŋ] adj.滞销的;动作缓慢的

We looked like a bunch of awkward kids riding a slow-moving carousel.

我们看起来就像一群骑在旋转木马上的笨拙的孩子。

(4)trench [trentʃ] n.沟,沟渠;战壕;堑壕 vt. 掘沟 vi.挖战壕;侵害

1.The soldiers trenched an outpost.

士兵们用战壕防御前哨。

2.A long narrow trench or furrow dug in the ground, as for irrigation, drainage, or a boundary line.

沟渠，排水沟，''。'水道'。''在地面上狭长的沟渠或细沟，用于灌溉、排水或用作分界线。