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  • 大陆漂移的磁极证据

    A magnetometer being used in oceanic research for studying continental drift.
     

    How did technology play a role in developing Wegener's idea?
    ::技术如何在发展韦格纳的想法中发挥作用?

    After Wegener's death, the   idea was pretty much dead. It would have remained that way except for the development of technology. Using technology, scientists would find more evidence that continents had drifted. They would also be able to find the  mechanism . This type of  magnetometer  was one of their important tools.
    ::维根纳死后,这个想法几乎就消失了。除了技术发展之外,它本来会一直如此。科学家们会利用技术找到更多大陆漂移的证据。他们也能找到这个机制。这种磁强计是他们重要的工具之一。

    Magnetic Polarity
    ::磁极

    Some important evidence for continental drift came after Wegener's death. The following is the magnetic evidence: Earth's  magnetic field  surrounds the  planet  from pole to pole. If you have ever been hiking or camping, you may have used a  compass  to help you find your way. A compass points to the magnetic North Pole. The compass needle aligns with Earth’s magnetic field.
    ::Wegener 死后, 出现了一些重要的大陆漂移证据。 磁证据如下: 地球磁场从极到极环绕着行星。 如果您曾经徒步远足或露营, 您可能已经使用指南针帮助您找到路。 指南针指向磁极北极。 指南针与地球磁场相吻合。

    Some   contain little compasses too! As  lava  cools, tiny iron-rich crystals line up with Earth’s magnetic field. These crystals are  magnetite  crystals. Anywhere lavas have cooled, these magnetite crystals point to the magnetic poles. The little magnets point to where the North Pole was when the lava cooled. A  magnetometer  is a device capable of measuring the magnetic field. A magnetometer can be used on land. A magnetometer also can be dragged behind a ship.
    ::随着熔岩冷却,微小的富铁晶体与地球磁场相连接。这些晶体是磁铁晶体。在熔岩冷却的地方,这些磁铁晶体指向磁极。这些磁铁晶体指向熔岩冷却时北极的位置。磁强计是一种能够测量磁场的装置。磁强计可用于陆地。磁强计也可以拖到船上后面。

    Evidence for Continental Drift
    ::大陆漂流的证据

    Geologists used magnetometers to look at rocks on land. They wanted to know which direction magnetite crystals pointed. This would tell them where magnetic north was at the time the rocks cooled. This is what they learned:
    ::地质学家用磁强计查看陆地上的岩石。 他们想知道磁铁晶体指向哪个方向。 这将告诉他们岩石冷却时北面的磁性位置。 这就是他们学到的:

    • Magnetite crystals in fresh  volcanic rocks  point to the current magnetic north pole ( Figure   ).
      ::新鲜火山岩中的磁铁晶体指向目前的磁性北极(图)。
    Map showing the North Magnetic Pole, Geographic North Pole, and North Geomagnetic Pole locations.
     
    Earth’s current north magnetic pole is over the Arctic Ocean between northern Canada and Siberia.
    • Older rocks that are the same age and are on the same  continent  point to the same  . However, the location they point to is not the current north magnetic pole.
      ::同一大陆上年老的岩石指向同一大陆。然而,它们指向的位置不是目前的北磁极。
    • Older rocks that are different ages and are on the same continent do not point to the same location. None of them point to the current magnetic north pole.
      ::古老的岩石年龄不同,位于同一大陆,但并不指向同一地点,没有一个指向目前的磁性北极。
    • Rocks on different continents that are the same age point to different locations. Only recent rocks point to the current north magnetic pole.
      ::不同大陆上的岩石都指向不同的地点,只有最近的岩石指向当前的北极磁极。

    The Earth’s magnetic north pole does shift slightly over time, but geologists did not believe that it could have moved as much as their observations of magnetite seemed to indicate.  It also seemed unlikely that there was more than one magnetic north pole in the past.  If the north pole hadn’t drastically changed locations, then the continents moving was a logical explanation.
    ::地球磁性北极确实随着时间推移而略有变化,但地质学家们并不认为它能移动到他们对磁铁的观测所显示的高度。 过去似乎也不太可能有不止一个磁性北极。 如果北极没有急剧改变位置,那么移动的大陆就是一个合乎逻辑的解释。

    Support for Wegener's Idea
    ::支持Wegener的理念

    Geologists tested the idea that the pole remained fixed but the continents moved. They fitted the continents together as Wegener had done. They moved them into the positions where they had been at the time the magnetite crystals cooled. The magnetite crystals pointed to the current north magnetic pole ( Figure   ). The magnetic pole seemed to have moved, but had not. They named the phenomenon  apparent polar wander .
    ::地质学家测试了两极保持固定但大陆移动的想法。 它们像 Wegener 所做的那样将各大洲连接在一起。 它们把它们移到磁铁晶体冷却时的位置。 磁铁晶体指向当前的北磁极( Figure ) 。 磁极似乎已经移动, 但没有移动。 它们给这个现象命名为明显的极地漫游。

    Maps showing apparent polar wander paths for continents indicating evidence for continental drift.
     
    On the left: The apparent North Pole for Europe and North America if the continents were always in their current locations. The two paths merge into one if the continents are allowed to drift.

    Geologists were now more interested in continental drift. More than ever, they needed a mechanism.
    ::地质学家现在对大陆漂移更加感兴趣,他们比以往任何时候都更需要一个机制。

     

    Summary
    ::摘要

    • Magnetite is a magnetic mineral found in lava. The magnetite points to the magnetic north pole when it cools.
      ::磁铁是熔岩中发现的磁矿 磁铁在冷却时指向磁性北极
    • Scientists used magnetometers to show where the north magnetic pole had been when magnetite crystals cooled.
      ::科学家使用磁强计显示磁铁晶体冷却时北磁极的位置。
    • Magnetite crystals of different ages and on different continents pointed to different spots. The simplest explanation is that the continents have moved.
      ::不同时代和不同大陆的磁铁晶体指向不同的地点,最简单的解释是大陆已经移动。
    • Apparent polar wander is another line of evidence for drifting continents.
      ::显而易见的极地漫游是漂流大陆的另一条证据。

    Review
    ::回顾

    1. What is apparent polar wander?
      ::什么是明显的极地漫游?
    1. Describe how magnetite indicates a magnetic pole. Why does it sometimes point to a spot that is not where the pole is located?
      ::描述磁铁如何表示磁极。 为什么它有时指向一个不位于电极位置的地方?
    1. How did scientists use magnetic evidence to conclude that the continents moved?
      ::科学家如何利用磁性证据 得出大陆移动的结论?