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  • Okay, we already know that there are water-bearing minerals within the Earth’s mantle

  • that are essentially deconstructed water.

  • But this time when we say there are giant reservoirs of water hiding deep under the ocean?

  • We mean fresh water, as you and I would recognize it. That we could drink.

  • Like, water-water.

  • About 2,800 cubic kilometers of it.

  • Just to emphasize how freaking big that is, that’s enough to fill over a billion Olympic swimming pools.

  • Or to put another way: it stretches not only the length of New Jersey’s coastline,

  • but also that of Massachusetts, Rhode Island, Connecticut, and most of New York.

  • Casual.

  • Oceanographic teams have known for a while that there are pockets of fresh water below the seafloor

  • they would run into them occasionally when drilling offshore for oil.

  • But when geologists and geophysicists started to explore how big these pockets actually are?

  • They were floored.

  • A collaborative team from Columbia University and Woods Hole Oceanographic Institution

  • used two different marine electromagnetic methods to pulse the seafloor.

  • One method involved deploying ten broadband electromagnetic receivers onto the actual seafloor,

  • which thenlookeddown to detect what lurks below.

  • The second method was to tow an antennae broadcasting a certain frequency behind a ship,

  • with electromagnetic receivers at four different depth levels.

  • These techniques rely on the fact that salt water is a much better conductor of electromagnetic waves

  • than fresh water is, allowing us to probe things that we can’t see visually,

  • like the composition of the Earth below the seafloor.

  • Scientists believe the water’s probably been there for a pretty long time.

  • When everything was frozen in the last Ice Age,

  • the sea levels were lower, so what is now this ocean floor was actually exposed,

  • and when the glaciers melted,

  • freshwater melt-off formed watersheds on the exposed ocean floor sediments,

  • eventually getting trapped there in huge pockets as sea levels rose again.

  • The water’s origin story may mean that aquifers like this could provide us with clues about the glaciers

  • and sea levels of the past.

  • But the team also believes that these undersea aquifers are being supplied with new freshwater

  • from subterranean systems.

  • Rising and falling ocean tides provide alternating pressure to deep onshore sediments,

  • acting a bit like an absorbent sponge, pulling underground water toward the ocean.

  • This means that the hydrologic systems under the land, many of which we already use,

  • may be connected to undersea aquifers in ways we didn’t previously know about.

  • Researchers hope that this discovery means this particular aquifer is not the only one of its kind,

  • and that they can use similar methods to find more.

  • And at this point you may be wondering: can we actually use this water?

  • The UN estimates there will be 9.7 billion people living on Earth by 2050,

  • and several countries, like India, are already suffering major water shortages.

  • As early as 2025, about half of the world’s population may lack as much fresh water as they need,

  • and maybe these newly discovered undersea aquifers could provide us with an unexpected solution.

  • But if we ever wanted to use this water for drinking, we would have to desalinate it,

  • as it does get a little saltyespecially the farther out into the aquifer you go.

  • It is much less salty than ocean water, though, making it less expensive and difficult to desalinate

  • and potentially giving us some hope when staring down an impending water crisis.

  • There’s cause for pause also, because new simulations have shown that because of the connection

  • between onshore hydrologic systems and undersea aquifers,

  • pulling water from under the ocean may then pull more water from under the land,

  • and could cause the ground to literally sink.

  • So before we can think of these surprisingly massive aquifers as usable resources,

  • a lot of thoughtand probably a lot of computer modelingis going to need to be put into

  • how we could access them and if we do, what the effects will be.

  • Are there other deep-Earth projects that would like us to cover?

  • Let us know in the comments.

  • And for more exciting discoveries, make sure to tune into Shark Week,

  • to dive into a whole week of shark content, starting July 28th on Discovery.

  • As always, thanks for watching, and we'll see you next time.

Okay, we already know that there are water-bearing minerals within the Earth’s mantle

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B2 中高級

科學家們剛剛發現了海底的淡水,而且規模很大。 (Scientists Just Discovered Fresh Water Under the Ocean, and It’s HUGE)

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    林宜悉 發佈於 2021 年 01 月 14 日
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