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  • On June 7, 1692, the Jamaican city of Port Royal, a notorious pirate haven, sank into

  • its own harbor.

  • This disaster (or blessing, depending on who you ask) was caused by liquefaction of the

  • ground following a major earthquake, and we know it happened at exactly 11:43 am thanks

  • to a pocketwatch that went down along with two thirds of the town and over 2000 people.

  • Liquefaction happens when waterlogged, loose soil (we call it "sand") turns into quicksand

  • - temporarily.

  • If you look closely at sand, you'll realize that it's actually comprised of tons of tiny

  • rocks, and their roundness and roughly uniform size mean there's space between them that

  • can get filled by water.

  • When we step on saturated sand at the water's edge, it's fairly stable because the particles

  • get pushed together and rest on each other, while any excess water escapes by flowing

  • away to where the pressure is lower.

  • We can (and do) build buildings on wet sandy soil, since the weight of the grains and the

  • friction between them makes the soil behave as a solid most of the time.

  • But in an earthquake, soil particles repeatedly jostle back and forth so much that the water

  • can't flow away.

  • Loosely packed dry soils tend to compress under stress, but with incompressible water

  • in the gaps between grains (which can't escape), the soil can't compress and the water takes

  • the load.

  • Unfortunately, water, as a liquid, doesn't have much structural integrity - so if the

  • saturated soil is forced to compress too much too quickly, it will start to act like a liquid,

  • and dense objects resting on the now liquefied soil will sink.

  • You can experience liquefaction for yourself in the water-soaked sand near the edge of

  • a beach - it feels pretty solid if you stand still, but if you wiggle your toes, the movement

  • causes the sand to liquefy beneath you, burying your feet.

  • On a larger scale, earthquake-induced liquefaction can swallow cars, roads, and even enormous

  • apartment complexes.

  • In other words, earthquakes can create quicksand, except that when the shaking stops and the

  • soil particles are no longer suspended in water, the ground solidifies again and anything

  • that sank becomes stuck.

  • Like this carrrrrr.

On June 7, 1692, the Jamaican city of Port Royal, a notorious pirate haven, sank into

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B1 中級 美國腔

这辆车发生了什么?(What Happened To This Car?)

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    joey joey 發佈於 2021 年 04 月 30 日
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