英语听力：探索发现 2014-06-29 BBC 地平线：陨石的真相-21

 Comparing the effects of an airburst with a ground strike, it seems the Chelyabinsk got away lightly. It’s estimated that the largest piece to hit the ground weighed 500 kilos, a fraction of the asteroid’s original mass of 7,000 tonnes. 

 

Now if a piece of rock that big had hit that area of Russia, it would have produced a huge impact crater¹. Then that kinetic² energy is then delivered into the ground and we see things like seismic³ shock. So, you get … people would feel earthquakes on the ground.

 

So the fact that it was an airburst actually limited the consequences for the people on the ground. So, yes, still quite dramatic, still, you know, obviously, causing injuries. But it could have been a lot worse, had it survived down to ground.

 

Ground strikes are amongst the most destructive natural hazards we know of. When viewed from space, Earth’s encounters with giant asteroids⁴ in its deep history are revealed. And there is evidence from our planet’s past of a truly devastating⁵ meteorite⁶ strike that decisively altered the course of life on Earth.   

 

Today millions of years after the impact, the evidence for that crater is well hidden. This is a gateway⁷ to the cenotes, the unique cave system of Mexico’s Yucatan Peninsula.

1 crater   

n.火山口，弹坑

参考例句：

• With a telescope you can see the huge crater of Ve-suvius.用望远镜你能看到巨大的维苏威火山口。
• They came to the lip of a dead crater.他们来到了一个死火山口。

2 kinetic   

adj.运动的；动力学的

参考例句：

• There exist many sources of energy both potential and kinetic.存在着许多势能和动能的能源。
• The kinetic theory of gases is the best known example.气体动力学理论就是最有名的例子。

3 seismic   

a.地震的，地震强度的

参考例句：

• Earthquakes produce two types of seismic waves.地震产生两种地震波。
• The latest seismic activity was also felt in northern Kenya.肯尼亚北部也感觉到了最近的地震活动。

4 asteroids   

n.小行星( asteroid的名词复数 )；海盘车，海星

参考例句：

• Asteroids,also known as "minor planets",are numerous in the outer space. 小行星，亦称为“小型行星”，在外太空中不计其数。
• Most stars probably have their quota of planets, meteorids, comets, and asteroids. 多数恒星也许还拥有若干行星、流星、彗星和小行星。

5 devastating   

adj.毁灭性的，令人震惊的，强有力的

参考例句：

• It is the most devastating storm in 20 years.这是20年来破坏性最大的风暴。
• Affairs do have a devastating effect on marriages.婚外情确实会对婚姻造成毁灭性的影响。

6 meteorite   

n.陨石；流星

参考例句：

• The meteorite in Jilin Exhibition Hall is believed to be the largest in the world.吉林展览馆的陨石被认为是世界上最大的。
• The famous Murchison meteorite smashed into the Australian ground in 1969.1969年著名的默奇森陨石轰然坠落在澳大利亚。

7 gateway   

n.大门口，出入口，途径，方法

参考例句：

• Hard work is the gateway to success.努力工作是通往成功之路。
• A man collected tolls at the gateway.一个人在大门口收通行费。