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  • 地壳

    Photos showing Earth's crust: continental crust above land and oceanic crust underwater.
     

    What do these two photos have in common?
    ::这两张照片有什么共同点?

    Both of these photos are of Earth's  crust . The crust on the left is on the  continent . It's what you see and walk on every  day . The crust on the right is in the ocean. You may have seen pictures, but to see it in person you need special equipment.
    ::这两张照片都是地球的地壳。左边的地壳是在大陆上。 这是你每天看到和走路的东西。 右边的地壳是在海洋中。 你可能看过照片, 但是要亲眼看到, 你需要特殊的设备。

    Crust
    ::结结结结

    Crust, mantle, and  core  differ from each other in chemical composition. It's understandable that scientists know the most about the crust, and less about deeper layers. Earth’s  crust  is a thin, brittle outer shell. The crust is made of  . This layer is thinner under the oceans and much thicker in  mountain  ranges.
    ::在化学成分方面,结壳、地壳和核心在化学成分上各不相同。 科学家最了解地壳,更不了解更深的层层,这是可以理解的。 地壳是一个薄的、易碎的外壳。地壳是由 . 地壳是由 . 这个层在海洋下更薄,在山脉中更厚。

    Oceanic Crust
    ::海洋结壳

    There are two kinds of crust.  Oceanic crust  is made of  mafic  lavas that flow onto the   and is mainly basalt ( Figure   ). It is relatively thin, between 5 to 12 kilometers thick (3 - 8 miles). The rocks of the oceanic crust are denser (3.0 g/cm 3 ) than the rocks that make up the continents. Thick layers of mud cover much of the ocean floor, which may eventually form  sedimentary rock .
    ::有两种地壳。海洋地壳是由流入地壳的岩浆熔岩组成,主要为岩浆(图)。相对薄,厚5至12公里(3-8英里)。大洋地壳的岩石密度(3.0克/立方厘米)比构成大陆的岩石密度(3.0克/立方厘米)高。厚厚的泥层覆盖了大部分洋底,最终可能形成沉积岩。

    A dark, dense rock specimen, likely representing gabbro from the oceanic crust.
     
    Gabbro is a dark dense rock that can be found in oceanic crust.

    Continental Crust
    ::大陆结壳

    Continental crust  is much thicker than oceanic crust. It is 35 kilometers (22 miles) thick on average, but it varies a lot. Continental crust is made up of many different rocks ( Figure   ). All three major rock types—igneous, metamorphic, and sedimentary—are found in continental crust, but the greatest proportion is made of  felsic    such as granite. On average, continental crust is much less dense (2.7 g/cm 3 ) than oceanic crust. Since it is less dense, it rises higher above the mantle than oceanic crust.
    ::大陆地壳比大洋地壳厚得多,平均为35公里(22英里)厚,但差异很大。大陆地壳由许多不同的岩石组成(图 )。所有三种主要的岩石类型都存在于大陆地壳中,有色、变形和沉积,但比例最大的是花岗岩,平均而言,大陆地壳的密度(2.7克/立方厘米)比大洋地壳低得多。由于地壳密度较小,它高于海壳。

    Quarry displaying layered rock formations, illustrating granite extraction from continental crust.
     
    The average composition of continental crust is granite.

     

    Summary
    ::摘要

    • Oceanic crust is thinner and denser than continental crust.
      ::海洋地壳比大陆地壳更薄、更稠密。
    • Oceanic crust is darker in color and denser (more mafic). Continental crust is lighter in color and density (more felsic).
      ::海洋地壳的颜色更暗,密度更稠密(更粗糙),大陆地壳的颜色和密度较轻(丰厚)。
    • Earth's crust is very thin relative to Earth's radius.
      ::相对于地球的半径 地球的地壳很薄

    Review
    ::回顾

    1. What are the properties of crust?
      ::地壳的特性是什么?
    1. Describe the properties of oceanic crust.
      ::描述大洋地壳的特性。
    1. Describe the properties of continental crust.
      ::描述大陆地壳的特性。

    Explore More
    ::探索更多

    Use this resource to answer the questions that follow.
    ::使用此资源回答下面的问题 。

    1. Where did Hurricane Harvey make landfall? How much water did it dump?
      ::哈维飓风在哪里登陆?
    1. Where did the water go after the storm?
      ::暴风雨过后水流到哪里去了?
    1. What happened to Earth’s crust?
      ::地球地壳怎么了?
    1. How can scientists determine the weight of the water from Harvey?
      ::科学家如何确定哈维的水的重量?
    1. What is depression of crust called?
      ::地壳萧条叫什么来着?
    1. Where did the water go after Harvey?
      ::哈维被水冲到哪里去了?
    1. How long did it take for the water stored on land to dissipate?
      ::储存在陆地上的水耗尽需要多长时间?
    1. Why will storms strike with increased frequency and ferocity?
      ::为什么暴风雨会更频繁、更凶猛地袭击?
    1. What does the narrator’s mom always say?
      ::旁白的妈妈总是说些什么?