英语听力：自然百科 地球力场 Earth's Force Field—13

 Glatsmire's model shows that the magnetic poles swap¹ places spontaneously due to / complex processes within the core. 

 

 

 

We were used to the idea that a compass points somewhere near the North Pole and hence we can use it for navigation, but there are periods in the past when the compass would have pointed² in exactly the opposite direction.

 

 

 

Glatsmire's research also suggests that there's a decline in the magnetic field strength before and after these reversals. Does this explain why the magnetic field is currently weakest beneath the South Atlantic? Are the magnetic poles about to reverse? 

 

 

 

We've never witnessed a reversal so we don't really know what would look like. We could guess and would almost surely take the bauble³ of the magnetosphere and contract/ it inward, closer to the surface of the Earth.

 

 

 

If this is the start of the magnetic field reversal, our planet will face increasing exposure to cosmic radiation for thousands of years to come. But so far, the random⁴ reversal of the Earth's magnetic field has only been seen inside a computer. For concrete evidence, scientists turn their attention to the volcanic⁵ islands of Hawaii. 

 

 

 

Locked inside this ancient lava⁶ is a pristine⁷ record of Earth's magnetic field stretching back millions of years. 

 

 

 

Professor Emilio Herrero-Bervera is searching for clues to Earth's magnetic past. 

 

 

 

One of the reasons why we are coming here is because we're looking for the lava floors that are relatively⁸ thin, you can see the boundary of this lava floor and these are all the boundaries. From here you see another one, and another one and another one, all these fantastic sequence of lava floors we're talking about 300 floors, 400 floors.

 

 

 

Molten lava from these island volcanoes accumulates over millions of years. When the lava flows hit the seawater, they cool rapidly, creating snapshots of Earth's magnetic field strength.

1 swap   

n.交换；vt.交换，用...作交易

参考例句：

• I will swap you my bicycle for your radio.我想拿我的自行车换你的收音机。
• This comic was a swap that I got from Nick.这本漫画书是我从尼克那里换来的。

2 pointed   

adj.尖的，直截了当的

参考例句：

• He gave me a very sharp pointed pencil.他给我一支削得非常尖的铅笔。
• She wished to show Mrs.John Dashwood by this pointed invitation to her brother.她想通过对达茨伍德夫人提出直截了当的邀请向她的哥哥表示出来。

3 bauble   

n.美观而无价值的饰物

参考例句：

• That little bauble is not to be compared with this enormous jewel.那个小摆设不能与这个大宝石相比较。
• A bauble is a showy ornament of little value.廉价珠宝是华而不实的装饰品。

4 random   

adj.随机的；任意的；n.偶然的(或随便的)行动

参考例句：

• The list is arranged in a random order.名单排列不分先后。
• On random inspection the meat was found to be bad.经抽查，发现肉变质了。

5 volcanic   

adj.火山的；象火山的；由火山引起的

参考例句：

• There have been several volcanic eruptions this year.今年火山爆发了好几次。
• Volcanic activity has created thermal springs and boiling mud pools.火山活动产生了温泉和沸腾的泥浆池。

6 lava   

n.熔岩，火山岩

参考例句：

• The lava flowed down the sides of the volcano.熔岩沿火山坡面涌流而下。
• His anger spilled out like lava.他的愤怒像火山爆发似的迸发出来。

7 pristine   

adj.原来的，古时的，原始的，纯净的，无垢的

参考例句：

• He wiped his fingers on his pristine handkerchief.他用他那块洁净的手帕擦手指。
• He wasn't about to blemish that pristine record.他本不想去玷污那清白的过去。

8 relatively   

adv.比较...地，相对地

参考例句：

• The rabbit is a relatively recent introduction in Australia.兔子是相对较新引入澳大利亚的物种。
• The operation was relatively painless.手术相对来说不痛。