- CίЕ(sh)ôk ]ȣ
- P(gun)]
и (tng) (tng)ôk
и (tng)ϤӢZ(y)ôk?
ڽиԇETSƳµ (tng)ͿZ(y)IJмӢ(gu)ĴԼmĿ횳J(rn)ڄ_(ki)ʼ֪@(g)׃(dng)СҲX(ju)ñ^@ġETS@ꌦ(du)иԇĸ׃ֶһЩ{(dio)ͬr(sh)Ҳ(hu)o³ֵm(yng)r(sh)g (tng)߸׃s](mi)κֱӾ_(ki)ʼƺЩǺ(li)См(x)һETSĕr(sh)һֱDZ^(yn)֔(jn)?sh)ģ?du)}}Ҳ@Ȼ˵ԒСJ(rn)˽o迼m(yng)r(sh)gи (tng)мʹ(ni)F(xin)(yng)ԓҲ(hu)̫(hu)(du)ҵijɿ(j)̫Ӱ
ETSҪ{(dio)?
(du)ETS@ĸ׃PX(ju)ÿԳ⡣@߀ǏČ(sh)иԇ@ô(jng)v˺Î״δ׃ԭҪ߀ϣ܉ͨ^(gu)иԇ˽ⱱУ@ČW(xu)g(sh)ĭh(hun)(gu)һ(g)Էdz(qing)ć(gu)(gu)ĴW(xu)HH(gu)Ľ߀Ӣ(gu)Լ(g)(gu)ҵĽԼv˸õW(xu)ǰm(yng)У@h(hun)ȥ(gu)܉ٵ_(ki)չW(xu)(x)@ӵĸ׃ҲͲˡ
Α(yng)(du)и (tng)еİ?
(du)Α(yng)(du)@һ׃䌍(sh)@(g)(wn)}ܺ(jin)?yn)鱾|(zh)ρ(li)f(shu)߀ǶӢZ(y)ԲeҲ(hu)e(du)ڿԇxF(xin)߀^h(yun)ͬW(xu)䌍(sh)B(yng)(du)ӢʽdȤȿһЩӢһЩӢʽLie to me֮ģȸһӢʽ֮̎ͨ^(gu) (tng)һЩo(j)ƬDŽeIJϣԼӢʽ (tng)ˮƽ;ԇühͲҪ̫r(sh)g@ˣETSṩsample (tng) (tng)ҪעӢʽӢZ(y)һЩ~ϸʽһą^(q)eҲHҪעҲҪע~Rϵļ(x)e
ڰĴmb@ɂ(g)(gu)ҸӢ(gu)ǧzf(wn)|(lin)ϵ@ɷNҲӢʽ^ӽһЩl(f)ϵą^(q)eֻҪھW(wng)һҎ(gu)ɣȻעͿ̫^(gu)ړ(dn)
и (tng)(x)(du)ı
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}ൽȺஔ(dng)?sh)ƽ?/p>
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^(q)Еr(sh)QԭЕr(sh)(Q)ɲԭs-t-e-p-p-e
The defining features are level terrain, dry climate, and an absence of trees.
͵ˮƽĵ(sh)Ě߀И(sh)ľȱ
The Great Plains are actually the former bed of a shallow inland sea.
ƽԭ(sh)ǰ\(ni)ꑺĺ
Over millions of years, sediment left by glaciers, water, and wind smoothed out the dry sea bed.
(sh)f(wn)ԁ(li)µijeˮL(fng)ѸĺŪƽ
As I said, the Great Plaints are bordered on the west by the Rocky Mountains.
f(shu)^(gu)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}֮סˁ(li)̫ƽ|M(jn)ıشij՚
Lighter, drier air passes over the mountains.
pһЩһЩĿ՚Խ^(gu)ɽ}
Until people intervened with irrigation and farms, only grass could grow on the dry, windy plain.
˂ùȺr(nng)(chng)A(y)֮ǰֻвL(zhng)ڸL(fng)ƽԭ
In fact, we can divide the Great Plains into three zones.
(sh)҂ܰѴƽԭֳ(g)^(q)
In the west, where it's driest and windiest, the grass is very short.
ﲢL(fng)Ǻܰġ
In the eastern zone, there's more rain and grass grows as high as 360 centimeters.
ږ|^(q)иˮL(zhng)_(d)360ס
In the middle third, there's a mix of grass species that grow to an intermediate height.
gĵ(g)(zone)һ(g)L(zhng)g߶ȵIJݵNĻw
и (tng)(x)(du)ı
Scientists are always on the lookout for alternative sources of energy.
ƌW(xu)ҿڌԴ
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˳f(shu)܉ṩеú̿ʯ
It's found in something called gas hydrate and, believe it or not, that's a kind of ice.
l(f)F(xin)ijNwˮ(Ė||)Ų㣬һN
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@Nˮڮ(dng)Y(ji)r(sh)(hu)º(ĵط)(hu)ںܴĉ֮(ԉܴ)
And trapped inside the crystals of ice are individual molecules of methane --- that's what's in natural gas.
ڱľwеdž(g)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(li)
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.
(dng)?sh)|(zh)W(xu)ҰһK@N()ρ(li)оr(sh)≺͜ضwˮ_(ki)ʼ˻˻ðݣڲ낀(g)Сr(sh)(ĕr(sh)g)ڻļ՚
Now, as you might guess, this can make gas hydrate kind of hard for miners to handle.
F(xin)ゃܲµģ@ʹwˮ(du)ڵV(li)f(shu)c(din)y̎
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(wn)}ڱıO^(q)x_(ki)_(d)һӢĺˮ
Environmentalists warn that mining it could even be disastrous.
h(hun)Ҿf(shu)_(ki)Ǟ(zi)yԵ
Offshore drilling could allow seawater to seep down into the huge icy deposits and release tons of methane up into the atmosphere.
x@̽ܕ(hu)ȻˮBıeጷşo(w)(sh)ļρ(li)M(jn)՚
And methane, our listeners may recall, is a greenhouse gas that could really worsen the problem of global warming.
ۂ (tng)(yng)ԓ(li)һNҚwĿʹȫ׃ůĆ(wn)}Ӑ
So, gas hydrate may offer some interesting possibilities.
wˮṩһЩP(gun)עİl(f)չԡ
But, with all these drawbacks, I'm not going to hold my breath waiting for it to fuel my furnace.
Sе@Щȱc(din)Ҳ(hu)סҵĺ(li)ȴȼҵĠt
и (tng) (tng)ôkP(gun)£
˼ (tng)ļ08-20
(tng)(gu)˼ (tng)10-03
2016и (tng)ָ(do)֮и (tng)c(din)11-02
и (tng)(jng)زľx08-11
и (tng)ԇ11-11
и (tng)08-23
и (tng)ָ08-17
и (tng)(jng)ԇ12-18