科学美国人60秒:Lightning May Sink Mountain Summits

Rocks are pretty tough, but eventually, even the mightiest mountains crumble. Geologists usually give the credit to water and ice. But when it comes to smashing summits, a major player may be electricity—in the form of lightning. Scientists have found evidence for lightning’s role in mangling mountains in the magnetic signatures of rocks, which go haywire when blasted by bolts.
 
“I mean, these magnetic anomalies are huge.” Susan Webb of the University of Witwatersrand in South Africa. “And so, we don’t expect to see that, not with ice fracturing rocks. We would see that only with lightning fracturing rocks. And the fact that there’s so many tells you that’s a really important mechanism for weathering rocks.”
 
Webb presented her results on December 18th at the annual meeting of the American Geophysical Union in San Francisco. [Susan Webb, Jasper Knight and Stefan Grab, Magnetic evidence for lightning strikes on mountains: a case study from Lesotho]
 
As a test case, she studied the magnetic signatures of rocks in the southern African country of Lesotho, a place with lots of mountains and lots of lightning. But Webb says she’s only scratched the surface. “And I think as we look more and more for this, and it’s very easy to look for if we do magnetic surveys in these areas, we will see it. Then we’ll be able to tell if this is a much more widespread phenomenon.”
 
—Julia Rosen
 
(The above text is a transcript of this podcast)