章节大纲

  • 常规

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  • 风沉积

    Lesson
    ::经验教训

     

    A comparison of sand dunes in Death Valley and desert pavement in Arizona.

     

    How does deposition by wind modify landscapes?
    ::风的沉降如何改变风景?

    On the right is a  desert   mountain  in Arizona. The surface in the foreground is  desert pavement . How did  wind  modify this  landscape ? On the left is a desert mountain with  sand dunes  in Death  Valley , California. How did wind modify this landscape?  Erosion  and deposition by wind leave very different landscapes behind.
    ::右边是亚利桑那州的一座沙漠山。地平面是沙漠路面。风是如何改变这片地貌的?左边是一座沙漠山,上面是加利福尼亚州死亡谷的沙丘。风是如何改变这片地貌的?风的侵蚀和沉积留下了完全不同的地貌。

    Wind Deposition
    ::风向沉积

    Like  water , when wind slows down it drops the  sediment  it's carrying. This often happens when the wind has to move over or around an obstacle. A   or tree may cause wind to slow down. As the wind slows, it deposits the largest particles first. Different types of deposits form depending on the size of the particles  deposited .
    ::就像水一样,当风慢下来时,它会下降它所携带的沉积物。当风必须移动或绕着障碍物移动时,这种情况经常发生。一棵树或一棵树可能会使风减慢。当风减慢时,它会先沉积最大的粒子。不同种类的沉积形式取决于沉积的粒子大小。

    Sand Dunes
    ::沙丘

    When the wind deposits sand, it forms small  hills . These hills are called  sand dunes  ( Figure   ). For sand dunes to form, there must be plenty of sand and wind. Sand dunes are found mainly in deserts and on  beaches .
    ::当风把沙子堆积起来时,沙子会形成小山,这些山被称为沙丘(图)。要形成沙丘,沙丘必须有足够的沙子和风。沙丘主要在沙漠和海滩上。

    A runner moves across sand dunes near a beach, with grass and ocean in background.

     

    A runner strides across sand dunes. Sand is picked up by her foot as it leaves the dune.
    ::沙丘上的沙子被她的脚捡起来 当它离开沙丘时

    How Sand Dunes Form
    ::沙丘如何形成

    What causes a sand dune to form? It starts with an obstacle, such as a rock. The obstacle causes the wind to slow down. The wind then drops some of its sand. As more sand is deposited, the dune gets bigger. The dune becomes the obstacle that slows the wind. This causes more sand to drop. The hill takes on the typical shape of a sand dune ( Figure   ).
    ::导致沙丘形成的原因是什么? 它始于一个障碍,如岩石。 障碍导致风减速, 风会降下一些沙子。 随着沙丘的沉积,沙丘会变大。 沙丘会成为拖慢风的屏障。 这会造成更多的沙子落下。 山会以沙丘的典型形状( 图示 ) 。

    Sand dune formation, highlighting wind direction and the slip face.

     

    A sand dune has a gentle slope on the side the wind blows from. The opposite side has a steep slope. This side is called the slip face.
    ::沙丘的侧面有一个温和的斜坡, 风从侧面吹来。 反面的侧面有一个陡峭的斜坡。 右侧称为滑雪脸 。

    Migration of Sand Dunes
    ::沙丘迁徙

    Once a sand dune forms, it may slowly migrate over the land. The wind moves grains of sand up the gently sloping side of the dune. This is done by  saltation . When the sand grains reach the top of the dune, they  slip  down the steeper side. The grains are pulled by gravity. The constant movement of sand up and over the dune causes the dune to move along the ground. A dune moves in the same direction that the wind usually blows. Can you explain why?
    ::沙丘形成后, 沙丘会慢慢地在陆地上移动。 风把沙粒移到沙丘的轻滑侧。 这是盐化的结果。 当沙粒到达沙丘的顶部时, 沙丘会滑落到更陡的侧面。 粒子会通过引力拉动。 沙丘的不断移动使沙丘沿着地面移动。 沙丘会向风通常吹向的方向移动。 你能解释为什么吗 ?

    Loess
    ::乐

    When the wind drops fine particles of silt and clay, it forms deposits called  loess  ( Figure   ). Loess deposits form vertical cliffs. Loess can become a thick, rich  soil . That’s why loess deposits are used for farming in many parts of the world.
    ::当风落下精细的淤泥和粘土粒子时,它会形成称为“浮渣”(图)的矿床。 低沉积形成垂直悬崖。 低沉的矿床会变成厚厚而富饶的土壤。 这就是为什么在世界许多地方,疏积的矿床被用来耕种。

    A winding path through loess hills with dry grasses under a clear blue sky.

     

    Loess hills in Missouri are home to the Squaw Creek Wildlife Refuge.
    ::密苏里州的Loess山是Squaw溪野生动物保护区的家园。

    Seafloor Mud
    ::海底泥泥

    Fine-grained mud in the deep ocean comes from silts and clays brought from the land by wind. The particles are deposited on the sea surface. they slowly settle to the deep ocean floor, forming brown, greenish, or reddish clays. Volcanic ash may also settle on the  .
    ::深海中精细的泥土来自由风从陆地带来的淤泥和泥土,微粒沉积在海面上,慢慢沉积在深洋底,形成棕色、绿色或红土。火山灰也可能沉积在海底。

    Summary
    ::摘要

    • The sand is transported until it is deposited in a sand dune.
      ::沙子被运到沙丘中,直到沉入沙丘。
    • Sand is blown up a slope. Gravity pulls it down the other side. This is how dunes migrate.
      ::沙子被炸向斜坡,重力将沙丘拉向另一侧,这就是沙丘迁移的方式。
    • Loess is very fine wind-blown deposits.
      ::劳斯是很好的风能矿床

    Review
    ::回顾

    1. Describe how wind deposits sediments as it slows.
      ::描述风能沉积如何减缓沉积。
    1. Describe how sand dunes move.
      ::描述沙丘如何移动。
    1. What is loess?
      ::什么是爱?

    Explore More
    ::探索更多

    Use the resource below to answer the questions that follow.
    ::利用以下资源回答以下问题。

    1. What size particles can wind move and why can't it move other sizes?
      ::风能移动什么大小的粒子, 为什么它不能移动其他大小的粒子?
    1. Why does wind erosion and deposition occur mostly in deserts?
      ::为什么风蚀和沉降主要发生在沙漠?
    1. Why does a stony pavement form in some desert areas?
      ::为什么在一些沙漠地区会有一条石路?
    1. What is a ventifact? Why is the ventifact in the video narrower at the base than the top?
      ::什么是心电图?为什么视频中的心电图比顶部更窄?
    1. What are sand dunes? Why are they usually made of quartz?
      ::什么是沙丘 为什么通常由石英制成
    1. What is cross bedding?
      ::什么是交叉床铺?