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  • 海底扩张假说

    Harry Hess, a naval officer and geology professor, examining equipment on a ship.

     

    How do the continents move?
    ::大陆如何移动?

    Harry Hess was a  geology  professor and a naval officer. He commanded an attack transport ship during WWII. Hess was intrigued by the     produced with the ship's  echo sounder . He thought about all of the evidence for  . He thought about all of the unusual features of the seafloor. And he found the  mechanism  to explain them all.
    ::哈里·赫斯是地质学教授兼海军军官。他在二战期间指挥了一艘攻击性运输船。赫斯被该船的回声声声响器所摄取。他思考了所有的证据。他思考了海底的所有异常特征。他找到了解释所有特征的机制。

    The Evidence Comes Together
    ::证据共聚一堂

    World War II allowed scientists to make some puzzling observations. The observations came from seafloor bathymetry and magnetism. These observations are:
    ::二次世界大战允许科学家进行一些令人费解的观察,这些观察来自海底水深测量和磁力学。

    • The seafloor has a large  mountain  range running through it. Deep  trenches  are found far from the ridges.  Guyots  have eroded tops that are deep below  sea level .
      ::海底有一大片山脉穿过它,深海沟远离海脊。海沟侵蚀了海平面深处的顶部。
    • The  magnetic polarity  of the seafloor changes. The center of the ridge is of  normal polarity . Stripes of normal and reverse polarity are found symmetrical on both sides of the ridge.
      ::海底变化的磁极性。 脊的中心是正常的极性。 在脊的两侧, 正常的和反向的两极均匀。
    • The youngest seafloor is at the ridge. The oldest is farthest from the ridge. The oldest seafloor is much younger than the oldest  continent .
      ::最年轻的海底位于海脊,最古老的海脊离海脊最远,最古老的海底比最古老的大陆要小得多。

    Scientists needed to explain these observations.
    ::科学家需要解释这些观察。

    Mantle Convection
    ::曼托对流

    Not long after Wegener's death, scientists recognized that there is  convection  in the mantle. Deeper material is hotter and so it rises. Near the surface, it becomes cooler and denser so it sinks. This creates a  convection cell  in the mantle.
    ::在韦格纳死后不久,科学家们就认识到地壳中有对流物。更深的物质更热,因此上升。在地表附近,它变得更冷,更稠密,因此沉没。这在地壳中形成了对流细胞。

    Seafloor Spreading
    ::海底平面平面

    After the war, Harry Hess put together the ideas and evidence he needed. Hess resurrected Wegener's continental drift  hypothesis . He reviewed the mantle convection idea. He thought about the bathymetric features and the patterns of magnetic polarity on the seafloor. In 1962, Hess published a new idea that he called  seafloor spreading .
    ::战争结束后,哈里·赫斯将他需要的想法和证据汇集在一起。赫斯恢复了韦格纳的大陆漂移假设。他回顾了地壳对流设想。他思考了海底的测深特征和磁极模式。1962年,赫斯发表了一个他称之为海底扩张的新想法。

    Hess wrote that hot  magma  rises up into the rift  valley  at the mid-ocean ridges. The  lava  cools to form new seafloor. Later more lava erupts at the ridge. The new lava pushes the seafloor horizontally away from the ridge  axis  ( Figure   ). The seafloor moves!
    ::Hes写道,热岩浆在洋中脊的裂谷中升起。熔岩冷却,形成新的海底。后来,火山熔岩在脊上喷发。新的熔岩将海底水平推离脊轴(Figure ) 。海底移动!

    Magnetite  crystals in the lava point in the direction of the magnetic north pole. The different stripes of magnetic polarity reveal the different ages of the seafloor.
    ::熔岩中的磁铁晶体指向磁性北极方向,磁极的不同条纹揭示了海底的不同年代。

    In some places, the  oceanic crust  comes up to a continent. The moving  crust  pushes that continent away from the ridge axis as well. If the moving oceanic crust reaches a deep sea trench, the crust sinks into the mantle. The creation and destruction of oceanic crust is the reason that continents move.
    ::在某些地方,海洋地壳来到一个大陆。移动的地壳将大陆推离脊轴。如果移动的海洋地壳到达深海战壕,地壳就会沉入地壳。海洋地壳的形成和破坏是大陆移动的原因。

    Magma rises from the mantle at mid-ocean ridges, creating new seafloor.

     

    Magma at the mid-ocean ridge creates new seafloor.
    ::洋中脊的玛格玛创造了新的海底。

    • As oceanic crust moves away from the ridge  crest , it pushes a continent away from the ridge axis.
      ::当海洋地壳从脊柱移开时, 它将大陆推离脊轴。
    • If the oceanic crust reaches a deep sea trench, it sinks into the trench.
      ::如果海洋结壳到达深海战壕,它就会沉入战壕。
    • The oldest crust is coldest and lies deepest in the ocean.
      ::最古老的地壳最冷 最深处是海洋

    The flat topped guyots were once  active volcanoes  that were above sea level. They were eroded at their tops. As the seafloor moved away from the ridge, the crust sank deeper. The tops of the guyots went below sea level.
    ::平板盖子曾经是海平面以上的活火山,在顶部被侵蚀。当海底从山脊移走时,地壳沉得更深。盖子的顶部低于海平面。

    The Mechanism for Continental Drift
    ::大陆漂流机制

    Seafloor spreading is the mechanism that Wegener was looking for! Convection currents within the mantle drive the continents. The continents are pushed by oceanic crust, like they are on a conveyor belt. Over millions of years the continents move around the planet’s surface. The spreading  plate  takes along any continent that rides on it.
    ::海底扩张是韦格纳所寻找的机制。 地壳内部的对流流流驱动着大陆。 大陆被海洋地壳所推动,就像它们在传送带上一样。 数百万年来,大陆环绕着地球表面移动。 扩张板块沿任何骑着它的大陆移动。

     

    Summary
    ::摘要

    • Seafloor spreading is a mixture different ideas and data. Continental drift and mantle convection are supported by bathymetric and magnetic data from the seafloor.
      ::海底扩散是一种混合的不同想法和数据,大陆漂移和地壳对流得到海底测深和磁数据的支持。
    • Harry Hess called his idea “an essay in geopoetry." This could be because so many ideas fit together so well. It could also be because, at the time, he didn’t have all the seafloor data he needed for evidence.
      ::哈里·赫斯将他的理念称为“地质诗篇文章 ” 。 这可能是因为很多想法都非常适合。 也可能是因为当时他没有他需要的全部海底数据作为证据。
    • Seafloor spreading is the mechanism for the drifting continents.
      ::海底扩散是漂流大陆的机制。

    Review
    ::回顾

    1. How does the pattern of magnetic stripes give evidence for seafloor spreading?
      ::磁带模式如何证明海底的扩展?
    1. How does the topography of the seafloor give evidence for seafloor spreading?
      ::海底的地形如何为海底的扩展提供证据?
    1. How does seafloor spreading fit into the idea that continents move about on Earth’s surface?
      ::海底扩散如何融入大陆在地球表面移动的想法?