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2018年3月SAT亚太考试内容回顾阅读五

2018-04-17 11:01:00 来源:网络SAT资料下载

   新东方在线SAT频道为大家带来2018年3月SAT亚太考试内容回顾阅读五一文,希望对大家SAT备考有所帮助。更多精彩尽请关注新东方在线SAT频道!

  第五篇:科学类

  科学家在月球的round hole下面发现了square peg,应该是一些lava。这些东西的存在标志着月球历史上有tectonic和volcanic activity.

  原文:

  Ancient magma plumbing found buried below moon'slargest dark spot

  By Eric HandOct. 1, 2014 ,1:00 PM

  Scientists have found a nearly squarepeg underneath a round hole—on the moon. Several kilometers below OceanusProcellarum, the largest dark spot on the moon’s near side, scientists havediscovered a giant rectangle thought to be the remnants of a geologicalplumbing system that spilled lava across the moon about 3.5 billion years ago.The features are similar to rift valleys on Earth—regions where the crust iscooling, contracting, and ripping apart. Their existence shows that the moon,early in its history, experienced tectonic and volcanic activity normallyassociated with much bigger planets.

  “We’re realizingthat the early moon was a much more dynamic place than we thought,” saysJeffrey Andrews-Hanna, a planetary scientist at the Colorado School of Mines inGolden and lead author of a new study of the Procellarum’s geology. Thediscovery also casts doubt on the decades-old theory that the circularProcellarum region is a basin, or giant crater, created when a large asteroidslammed into the moon. “We don’t expect a basin rim to have corners,”Andrews-Hanna says.

  The work isbased on data gathered by GRAIL (Gravity Recovery and Interior Laboratory), apair of NASA spacecraft that orbited the moon in 2012. Sensitive to tinyvariations in the gravitational tug of the moon, GRAIL mapped densityvariations below the surface (because regions of higher density produceslightly higher gravitational forces). Below known impact basins, GRAIL foundthe expected ringlike patterns, but underneath the Procellarum region, themysterious rectangle emerged. “It was a striking pattern that demanded anexplanation,” Andrews-Hanna says.

  Scientistsalready know that the Procellarum region is rich in radioactive elements thatbillions of years ago would have produced excess heat. The study team theorizesthat as this region cooled, the rock would have cracked in geometricalpatterns, like honeycomb patterns seen on Earth in basalt formations, but on amuch larger scale. In a study published today in Nature, the researcherspropose that these cracks eventually grew into rift valleys, wheremagma from the moon’s mantle welled up and pushed apart blocks of crust. Lava spilledout and paved over the Oceanus Procellarum, creating the dark spot that is seentoday. The extra weight of this dense material would have caused the wholeregion to sink slightly and form the topographic low that has made theProcellarum seem like a basin.

  With thediscovery, the moon joins Earth, Mars, and Venus as solar system bodies withmapped examples of rifting. There are also similar features near the south poleof Enceladus, the moon of Saturn that is spewing water into space from cracksin an ice shell.

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