The Future of Glaciers: Crash Course Geology #19 · CrashCourse
本集介绍冰川的形成、作用及其对环境和历史的影响。适合练习地理词汇和自然现象描述。
Tens of thousands of years ago, gigantic beasts roamed the earth.
数万年前，地球上生活着一些巨大的野兽。
Ones way bigger than woolly mammoths or dinosaurs.
它们的体型比长毛猛犸象或恐龙都要大得多。
They were big enough to dig out
它们的体积足够大，可以用来挖掘（某些东西）。
this massive lake, cause these giant scratches in the ground, and drop these boulders in the middle of a field.
这个巨大的湖泊在地面上留下了深深的痕迹（即那些巨大的“划痕”），同时还把一些巨石抛到了田野的中央。
And the best part?
最棒的部分是什么呢？
Some of those big guys are still out here today.
那些曾经叱咤风云的巨头中，有些人至今仍然活跃在商界或各个领域中。
I’m talking about...
我指的是……
glaciers!
冰川啊！
Hi!
嗨！
I’m Sage, and this is Crash Course Geology.
我是赛奇（Sage），这是《地质学速成课程》（Crash Course Geology）。
[THEME MUSIC] Glaciers are enormous masses of ice and snow that flow under their own weight, moving very slowly across the earth.
【主题音乐】冰川是由巨大的冰块和积雪构成的物质，它们在自身重量的作用下缓慢移动，横穿地球表面。
Or, at a glacial pace.
或者，以极其缓慢的速度。
As Miranda Priestly would say, “You know how that thrills me.”
正如米兰达·普里斯特利会说的那样：“你知道这让我有多兴奋吧。
And they’re not just boring hunks of ice.
它们可不仅仅是那些令人乏味的冰块罢了。
Glaciers provide habitats, hold over half of the world’s freshwater, and preserve hundreds of thousands of years worth of history within their layers.
冰川为许多生物提供了栖息地，储存了全球超过一半的淡水，并在其冰层中保存了数十万年的历史遗迹。
Glaciers are important to the spiritual beliefs of indigenous peoples, from Peru to China to Tanzania.
从秘鲁到中国，再到坦桑尼亚，冰川对当地原住民的精神信仰具有重要意义。
Plus, they’re stunning.
而且，它们美得令人惊叹。
Like, come on!
拜托！
How is that real?
那怎么可能是真的呢？
And they’re massive.
而且它们的体积非常庞大。
So, how does all that ice get there?
那么，所有那些冰究竟是如何到达那里的呢？
Well, it’s a little more complicated than a giant slush pile getting shoved to the edge of a Target parking lot.
嗯，这件事其实比把一大堆冰沙堆到塔吉特（Target）超市停车场的边缘要复杂得多。
Glaciers form when tons of snow falls in an area that’s so cold, the snow never totally melts.
冰川的形成过程是这样的：当大量积雪降落在气温极低的地区时，这些积雪永远不会完全融化。随着时间的推移，不断积累的雪层最终会压缩成冰川。
It starts to accumulate year after year, building up until the pile is huge— tens of meters deep,
这些物质年复一年地不断积累，最终形成了一座巨大的堆积物——厚度可达数十米。
and around 4050 square meters in area.
占地面积约为4050平方米。
And when there’s that much snow in one place, it gets so heavy, its frosty base starts to transform.
当一个地方积雪如此之多时，雪的重量会变得极其巨大，以至于其冰冻的底部开始发生变化（即开始融化或发生其他物理状态的变化）。
First, the snow at the base gets packed so tightly it turns into a state called firn, which is technically still snow.
首先，积雪在底部会被压实得非常紧密，从而形成一种被称为“粒雪”（firn）的状态。从技术上讲，这种状态仍然属于雪的范畴。
But while fresh snow is about 90 percent air, firn is only about 25 percent.
不过，新鲜雪的成分中约90%是空气，而粒雪（firn）的成分中只有约25%是空气。
That tightly-packed state gets us ready for the next transformation.
这种高度密集的状态为我们下一次的转变做好了准备。
With increasing pressure, the snow recrystallizes, trading its six-armed snowflake shape for dense, rounded crystals of firn that can grow bigger over time.
在压力不断增加的情况下，雪会重新结晶，其原本呈六边形结构的雪花形态会转变为致密、圆形的雪粒（即“firn”）。这些雪粒会随着时间的推移逐渐变大。
The ice is so dense, it absorbs every color of light except for blue, which is what gives glaciers their haunting glow.
冰的密度非常高，能够吸收所有颜色的光，唯有蓝色光能够穿透冰层。正是这种蓝色光赋予了冰川那种令人难忘的、幽暗的光泽。
That’s the basic process, but it doesn’t always look exactly the same.
这就是基本流程，不过实际情况并不总是完全相同的。
Glaciers are super varied in size and shape.
冰川在大小和形状上差异巨大。
Like, you’re probably familiar with continental glaciers: thick domes of ice that stretch thousands of square meters across Earth’s surface.
你可能对大陆冰川比较熟悉：那些厚厚的冰层呈圆顶状分布，覆盖面积可达数千平方公里。
Sometimes called ice sheets, these vast, frosty expanses exist in only two places today: Greenland and Antarctica.
这些广阔的、被冰雪覆盖的区域有时也被称作“冰盖”，如今它们仅存在于两个地方：格陵兰岛和南极洲。
But alpine glaciers, or mountain glaciers, are found on every continent except Australia.
不过，高山冰川（即位于山区的冰川）分布在除澳大利亚以外的所有大陆上。
Although, the Kiwis know there are glaciers in New Zealand.
尽管新西兰人知道新西兰境内存在冰川，但他们可能并不十分了解这些冰川的具体情况或分布范围。
I’m sorry, I don’t know why I thought I could do that.
对不起，我不知道自己为什么会认为自己能够做到那件事。
True to their name, alpine glaciers form high up on mountains in bowl-shaped formations called cirques— which the glaciers carve themselves!
正如其名称所示，高山冰川形成于高山深处，呈碗状的结构，这些结构被称为“冰斗”（cirques）——而冰川正是通过自身的侵蚀作用形成了这些冰斗。
If enough ice builds up, these can flow down as valley glaciers.
如果积冰量足够多，这些冰块就会以山谷冰川的形式向下流动。