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rg2022-10-12 20:21:46 иԇ ҪͶ

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ڽиԇETSƳµ ͿZIJмӢĴԼmĿ횳Jڄ_ʼ֪@׃ӺСҲXñ^@ETS@ꌦиԇĸ׃󲿷ֶһЩ΢{ͬrҲo³ֵmrg ߸׃s]κֱӾ_ʼƺЩʡǺСмһETSĕrһֱDZ^֔}}Ҳ@Ȼ˵ԒСJ˽o迼mrgи мʹݣFԓҲ̫ҵijɿ̫Ӱ푡

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ETS@ĸ׃PXÿԳ⡣@߀ǏČ֣иԇ@ôv˺Î״δ׃ԭҪ߀ϣ܉ͨ^иԇ˽ⱱУ@ČWgĭhһԷdzćңĴWHHĽ߀Ӣģ޵ԼҵĽԼv˸õ׌WǰmУ@hȥ܉ٵ_չW@ӵĸ׃ҲͲ

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Α@һ׃䌍@}ܺ鱾|ρf߀ǶӢZԲeҲ؄e󡣌ڿԇxF߀^hͬW䌍BӢʽdȤȿһЩӢһЩӢʽLie to me֮ȸһӢʽ֮̎ͨ^ һЩoƬDŽeIJԼӢʽ ˮƽ;ԇühͲҪ̫rg@ˣETSṩsample ͸ СҪעӢʽӢZһЩ~ϸʽһą^eҲHҪעҲҪע~Rϵļ΢e

ڰĴmb@ɂҸӢǧzf|“ϵ@ɷNҲӢʽ^ӽһЩlϵą^eֻҪھWһҎȻעͿ̫^ړ

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Look at our topographical map and you'll see that the middle third of the North American continent from the Rocky Mountains almost to the Mississippi River is pretty flat.

ۂ'ΈD㌢ꑵg֮һɽ}ൽȺஔƽ

This is the Great Plains.

@Ǵƽԭ

This kind of area is sometimes called a prairie, sometimes a steppe. That's s-t-e-p-p-e.

@N^ЕrQԭЕr(Q)ɲԭs-t-e-p-p-e

The defining features are level terrain, dry climate, and an absence of trees.

͵ˮƽĵ؄Ě߀Иľȱ

The Great Plains are actually the former bed of a shallow inland sea.

ƽԭŒǰ\ꑺĺ

Over millions of years, sediment left by glaciers, water, and wind smoothed out the dry sea bed.

fԁµijeˮLѸĺŪƽ

As I said, the Great Plaints are bordered on the west by the Rocky Mountains.

f^ǘƽԭͬɽ}

And it's really the Rockies that are responsible for the formation of the grasslands.

ɽ}γɲԭԭ

The mountains are so high that they block the heavy moist air traveling eastward from the Pacific Ocean.

ɽ}֮סˁ̫ƽ|Mıشij՚⡣

Lighter, drier air passes over the mountains.

pһЩһЩĿ՚Խ^ɽ}

Until people intervened with irrigation and farms, only grass could grow on the dry, windy plain.

˂ùȺrA֮ǰֻвLڸLƽԭ

In fact, we can divide the Great Plains into three zones.

Œ҂ܰѴƽԭֳ^

In the west, where it's driest and windiest, the grass is very short.

ﲢLǺܰ

In the eastern zone, there's more rain and grass grows as high as 360 centimeters.

ږ|؅^иˮL_360ס

In the middle third, there's a mix of grass species that grow to an intermediate height.

gĵ(zone)һLg߶ȵIJݵNĻw

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Scientists are always on the lookout for alternative sources of energy.

ƌWҿڌԴ

Today we're going to discuss one that's so plentiful they say it could supply more energy than all the coal and oil in the world.

҂̽ӑһN˳ģf܉ṩеú̿ʯ͸

It's found in something called gas hydrate and, believe it or not, that's a kind of ice.

lFijNwˮ(Ė||)ŲһN

That's right. But the water in this ice was way down below the Earth's surface when it was frozen, so it was under a lot of pressure.

ǵ@NˮڮYrº(ĵط)ںܴĉ֮(ԉܴ)

And trapped inside the crystals of ice are individual molecules of methane --- that's what's in natural gas.

ڱľwеdž΂ļӡ@Ȼ

All this makes gas hydrate pretty strange stuff.

@Щ(r)ʹÚwˮ(ɞ)ԎĖ|

If you touch a match to a piece of this ice, it'll burst into flame.

һ|@ӵһKϣһȼ

And when geologists bring a chunk of it up to the surface to study at normal air pressure and temperature, gas hydrate begins to hiss and bubble, and in less than half an hour, the ice melts and the methane inside escapes into the air.

|WҰһK@N()ρоr≺͜ض£wˮ_ʼ˻˻ðݣڲ낀Сr(ĕrg)ڻļ՚

Now, as you might guess, this can make gas hydrate kind of hard for miners to handle.

Fゃܲµģ@ʹwˮڵVfcy̎

And then there's the problem of where it's located in frozen arctic regions or in ocean waters off the Atlantic coast, and up to a mile down.

Ȼ̎λõĆ}ڱıO؅^x_󺣰_һӢĺˮ

Environmentalists warn that mining it could even be disastrous.

hҾf_ǞyԵ

Offshore drilling could allow seawater to seep down into the huge icy deposits and release tons of methane up into the atmosphere.

x@̽ܕȻˮBıeጷşoļρM՚

And methane, our listeners may recall, is a greenhouse gas that could really worsen the problem of global warming.

飬ۂ ԓһNҚwĿʹȫ׃ůĆ}Ӑ

So, gas hydrate may offer some interesting possibilities.

wˮṩһЩPעİlչ

But, with all these drawbacks, I'm not going to hold my breath waiting for it to fuel my furnace.

Sе@ЩȱcҲסҵĺȴȼҵĠt

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