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板块构造说 – 译学馆
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板块构造说

Plate Tectonics Explained

板块定期结合在一起,定期分开的大陆漂移学说
The idea that our planet’s continents drift around the globe, periodically glomming together
已经有至少200年的历史了。但是大多数地质学家在二十世纪六十年代之前
and breaking apart, is at least 200 years old. But most geologists didn’t believe
都不相信这个学说 ,直到越来越多的证据表明
it until the 1960’s, when mounting evidence made it clear that the Earth’s crust is
地壳分解成了许多移动的碎片,而这些碎片就是板块,可移动的板块。
broken up into fragments, and that those fragments, called tectonic plates, are moving. And these
现在我们可以从空间上直接以1毫米的精确度来追踪板块运动
days we directly track that motion – with millimeter precision – from space.
通常,对于板块运动的简单解释是
The common, simplified explanation for why tectonic plates are moving is that they’re
它们被上地幔也就是地壳岩石圈下面的一层缓慢流动的物质携带着
carried along on currents in the upper mantle, the slowly flowing layer of rock just below
向一点集中的流动物质使板块聚合在一起
Earth’s crust. Converging currents drive plates into each other; diverging currents
分散的流动物质把它们拉断
pull them apart.
这是很普遍的事实;地幔热的岩石来自地核并且在地壳下方移动
This is mostly true; hot mantle rock rises from the core and moves along under the crust
直到冷却固结然后又沉下去。 但是板块不仅仅是被动的
until it grows cool and heavy and sinks back down again. But the plates aren’t just passively
像一堆手提箱那样按照要求在传送带上运输
riding these conveyer-belt-like currents around like a bunch of suitcases at the baggage claim.
他们并不会这样,因为一些板块移动得比在它们下方的热流快
They can’t be, because some of the plates are moving faster than the currents underneath
例如,纳斯卡板块-南极洲板块的一部分
them. For example, the Nazca plate – a chunk of ocean crust off the west coast of South
每年向东移动10厘米距离 而地幔暖流的流动速度
America – is cruising eastward at about 10cm per year, while the mantle underneath
仅仅为每年五厘米。不管是板块还是行李
it oozes along at just five. Neither tectonic plates nor luggage can move faster than the
比它们各自“传送带”的速度更快。除非有什么东西拉伸或者挤压它们。
belt they’re riding on unless something else is helping to push or pull them along.
部分大陆板块被证实是受到了拉力。
And some of Earth’s plates, it turns out, are pulling themselves.  When an ocean plate
当一个海洋板块与另一个海洋板相碰撞或者一个板块与厚厚的地壳上的大陆板块相挤压,
collides with another ocean plate or a plate bearing the thick crust of continental landmasses,
两个板块中薄的一个将会弯曲并且滑到另一个的下方。随着海底的边缘
the thinner of the two plates bends and slides under the other. As the edge of the seafloor
陷入到地幔中,它会拉动它后面的板块,他会以像这条悬挂的链一样
sinks into the mantle, it pulls on the plate behind it, the same way a chain dangling further
从桌子上下降的速度越来越快,最后开始滑动。陷入的板块面积越大,
and further off a table will eventually start to slide. The bigger the sunken portion of
它给的拉力就越大,它后面剩余的板块就移动得越快。
the plate becomes, the harder it pulls and the faster the remaining plate behind it moves.
你可以通过看谷歌地球来找出这种现象发生在何处——非常深的、
You can find where this is happening by looking at google earth – the incredibly deep, narrow
一些大陆边缘的海岸边可见的狭窄的海沟,并且随着海洋板块向下运动
ocean trenches visible off the coasts of some continents and island chains mark the creases
海岛链标志着褶皱形成,在这个过程中将邻板块的边缘挤压弯曲。
formed as ocean crust plunges downward, bending the edge of its neighbor in the process.
而且,这些面积大块的海床帮助它们下面的
What’s more, those chunks of seafloor are actually helping to drive convection in the
地幔的气体对流。地壳上的岩石使陷入地壳的岩石向一侧移动
mantle beneath them. Sunken slabs of ocean crust block flowing rock from moving further
强迫它们向下运动和沉没。最后,这些板块因压力过大
sideways, forcing it to turn downward and sink. Eventually those slabs get too heavy
而断裂,朝着地核慢慢下陷,并且产生一股拉力
and break off, plunging slowly toward the core and creating a suction force that pulls
拉着下陷途中在它后面的地幔中的物质。因此,在某个方面来说,比起海床只是一个在地壳表面运动的物体
mantle material along behind it. So, in some ways, seafloor crust really is more like part
它更像是传送带的一部分。另外,
of the conveyor belt than something riding on top of it. The continents, on the other
大陆州就是传送带上的行李。
hand, are baggage.

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