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Thanks to Skillshare for supporting this episode of SciShow.
感谢Skillshare对本期《科学秀》的支持。
You've seen cartoons. You understand avalanches. There's fresh snow. Someone can't keep their voice down.
大家看过动画，知道雪崩是什么样的：下初雪，然后有人扯着嗓子喊。
Snow rumbles down the mountain and buries everything.
山上的雪隆隆倾下掩埋了一切。
Then everybody digs themselves out, they learn their lesson, and then they get hot chocolate.
然后大家把自己挖出来，他们吸取了教训，然后他们喝上了热可可。
Except, that's really not how it works at all. Real avalanches are much more dangerous.
但事实并非如此。真正的雪崩要危险得多。
And even though a single skier can trigger one, the classic avalanche set off by a loud yell probably never happens,
虽然一名滑雪者可以触发一场雪崩，但大叫声触发雪崩或许永远不可能发生，
because skiers create a lot more pressure than your voice, no matter how loud you yell.
因为滑雪者所造成的压力比声音要多得多，你叫多大声也没用。
Just about the only thing cartoons get right is that avalanches happen on snowy mountains.
卡通里只有一件事是正确的：雪崩发生在皑皑雪山中。
Snow builds up until it's nearly heavy enough to overcome the friction between it and what lies underneath
雪花堆积直至雪堆的重量足以克服雪和底部之间的摩擦。
Then, with the slightest extra push, that snow starts sliding down the slope. And once it gets going, you have yourself an avalanche.
然后在轻微的额外压力之下，积雪开始从斜坡滑下来。积雪一旦开始下滑，雪崩就有了。
The big ones can include up to millions of kilograms of snow, and can scream down a mountain as fast as 150 kilometers per hour.
大雪崩包括多达上百万千米的积雪，并且其从雪山呼啸而下的速度快达150千米每小时。
But there's more than one type of avalanche, and each one unfolds in its own hardcore way.
但是雪崩类型不止一种，并且每一种都有其绝对的呈现方式。
Powder avalanches, also called "loose-snow avalanches", are kind of exactly what they sound like.
粉雪崩，也被称为“松雪崩”，正如它们的名字一样。
They can happen after relatively loose snow falls on snow that's more densely packed.
它们通常发生在相对松散雪花堆积在密实堆积的积雪之上后。
If the denser snow has been there for at least a few days, it can be covered with a thin layer of hard frost called surface hoar.
如果密集积雪已经堆积了至少几天，那么就会被覆盖上一层薄薄的黑霜，即地面霜。
It keeps the new snow from mixing with the denser stuff underneath.
这层地面霜会阻止新雪和底层密集雪相混合。
The result is two distinct layers, where the top is pretty loose and the bottom is more dense and stable.
结果就形成了两层独特的层面，顶层相当松散，底层更加密集且牢固。
It only takes something small, like shifting snow or a skier, to overcome the friction between the two layers.
只要一些小小事物，比如高吹雪或一名滑雪者，就可以克服两个层面之间的摩擦。
And that sends some of the loose snow tumbling down. The snow stays pretty loose, falling more like a big cloud than a snowball.
导致一些松散雪倾塌。积雪仍相当松散，滚落时更像是一层巨大的云朵而非雪球。
But don't let the cloud simile fool you, there's still a lot of snow.
但是不要让云朵的比喻骗到你啦，其实积雪仍然非常多。
Powder avalanches can tear roofs off houses and even obliterate thick cement walls.
粉雪崩可以将屋顶与房屋分离，甚至可以摧毁厚厚的水泥土墙。
That said, if you're the skier who triggered one, you'll probably be okay.
即便如此，如果你是那个触发雪崩的滑雪者，你或许可以幸免。
Powder avalanches tend to start relatively small, only picking up more snow and becoming really dangerous as they move down the mountain.
粉雪崩开始时相对较小，只是慢慢堆积更多的雪，当它们滚下山时就成为了真正的危险。
Then there are slab avalanches, which account for about 90% of avalanche fatalities.
然后是板状雪崩，90%的雪崩伤亡都是由这种雪崩引起的。
They also start with two unmixed snow layers, but this time, their positions are reversed: the bottom layer is weaker, and the top is more dense.
它们也是从两个未混合的雪层开始的，但是这一次，它们的位置相反：底层薄弱，顶层更加密集。
Just like before, it only takes a small disturbance to get the top layer sliding along the bottom, or even right against the ground, if it's smooth enough.
正如之前一样，仅需一个小小的骚乱就可以让顶层积雪沿着底层滑落，或者如果地面足够顺滑的话，甚至可以正抵着地面滑落。
But because the sliding layer is stronger this time, it doesn't break up into a cloud. It stays together in one or a few huge chunks, called slabs.
但是由于这一次的滑动层更加坚硬，它不会分解成云状物。它会聚在一起形成一个或几个巨大的大块，即板状雪崩。
Each slab is like a densely packed snowball up to a meter deep and potentially hundreds of meters wide,
每个大块就像是密实填集的雪球一样，深达一米且可能有数百米宽，
and it can crush anyone unlucky enough to get in the way.
它可以摧毁任何一个挡路的倒霉蛋。
The slabs can also break free far from whatever triggered them in the first place,
板状雪崩还可以冲破任何远离触发物的事物，
thanks to a sort of ripple effect where clumps of snow pull on one another.
这还多亏了某种连锁反应，块状积雪相继落下。
And that's another reason they're so much deadlier than powder avalanches:
它们比粉雪崩更加致命的另一个原因是：
Even if you're far from the trigger point, you could still be standing on the slab that's about to fall.
即使你距离触发点很远，你仍有可能挡着将要倾落的雪块的路了。
Both kinds of avalanches can be started by a little extra pressure on the snowy surface,
两种雪崩都可以被积雪表面额外的小压力所触发，
anything from falling rocks to an avid snowmobiler going over the wrong spot at the wrong time.
比如落石或在错误时间出现在错误地点的驾雪车者。
So it seems to make sense that sound could trigger an avalanche. After all, sound travels as pressure waves, where molecules push against each other.
声音可以触发雪崩似乎有道理。毕竟，声音通过压力波传播，压力波中的分子相互推撞。
So you'd think a loud enough sound could provide that extra pressure to start an avalanche.
所以你认为足够大的声音可以造成额外压力导致一场雪崩。
And that is true, in principle. Shockwaves from dynamite are used to set off intentional avalanches so skiers can't start them accidentally.
原则上没错。炸药的短波可以用来触发蓄意雪崩，因此，滑雪者无法不慎触发它们。
But the classic picture of a gunshot or a scream triggering an avalanche is generally impossible.
但是射击的经典画面或一声尖叫触发雪崩的画面通常是不可能的。
Even if loud sounds hurt your ears, they usually have less than one hundredth the pressure they'd need to affect huge masses of snow.
即便是大喊大叫声伤到了你的耳朵，它们通常也不足影响大面积积雪所需压力的百分之一。
After all, think of the loudest sound you've ever heard: concerts, airplanes, infants, whatever.
毕竟，想想你听过的最吵闹的声音：音乐会、飞机、婴儿之类的。
Now think about how much that sound physically squeezed your body.
现在再想想这类声音对你身体造成的压力有多大。
Not how much your ears hurt, but how much your body was actually pushed and pulled by the sound itself,
不是声音对你耳朵造成了多大的伤害，而是声音本身对你的身体造成了多少的压力，
like when you feel the beat of a drum in your chest during a concert.
就像是在演唱会上，鼓声对你胸腔的感觉。
Now, compare that feeling to a fully equipped skier jumping on your stomach.
现在把那种感觉和一个全副武装的滑雪者扑向你胃部的感觉相对比。
The skier wins, and that's why they can trigger avalanches but loud sounds normally can't.
滑雪者赢了，因此他们可以触发雪崩而巨大的声响通常不行。
Even sonic booms, the shock waves that happen when something like a plane breaks the sound barrier, tend to be too quiet.
即便是超音波爆声（当飞机之类的事物打破了声障时就会发生冲击波）也太安静了。
Although over just the right combination of snow layers, they can sometimes nudge things past the tipping point.
虽然只是雪层的正确组合，但它们有时可以推动事物穿过引爆点。
So if you're ever on a slope and you're worried about an avalanche, you can shout at someone about it, just don't go jumping around on the mountain.
所以如果你站在滑坡处，担心发生雪崩的话，你可以冲着别人喊叫告诉他们，只要不在山上跳来跳去就行了。
But also, general tip: If you're really worried about an avalanche, maybe don't go on that mountain.
但提示一下：如果你真的担心雪崩的话，还是不要去雪山的好。
Whether I'm hiking in the mountains here in Montana or just biking around town, I'm always looking for new ways to film the world around me.
不论是在蒙大纳的山上徒步旅行还是骑脚踏车，我总在寻找拍摄周围世界的新方法。
And that's why I really like this Skillshare class by photographer Reuben Krabbe.
所以我真的很喜欢摄影师Reuben Krabbe的Skillshare课程。
It's called Adventure Sport Photography, and it teaches you the basics of how to shoot and edit amazing action shots,
课程名为Adventure Sport Photography，该课程教授摄影和编辑动态照片的基本技巧，
including some tips that could seriously help you out on your next ski trip.
包括一些帮助你决定下一次滑雪之旅的建议。
If you're headed to the mountains this winter, you're in luck:
如果你这个冬天要去雪山，那你走运了：
Right now, Skillshare is offering SciShow viewers 2 months of unlimited access for free.
现在Skillshare为《科学秀》的观众提供两个月的免费权限。
That means you could take this class, or any other of Skillshare's more than 20,000 classes, all while supporting SciShow.
也就是说你可以参与这门课程或是Skillshare上的其他任一课程，同时也是支持《科学秀》。
You can follow the link in the description to take advantage of this offer!
点击下方链接好好利用本次福利！
