Snow on lower mountain slopes can be a major challenge for any of the animals that live there.
低海拔山坡上的雪，是任何生活在那里的动物的一大挑战。
On the high peaks, however, really heavy snowfalls can be lethal.
然而在较高的顶峰，大量降雪却可能致命。
The rockies in North America. They rise to heights of over 4,400 metres.
位于北美的落基山脉。山峰可以超过4400米高。
In the winter, the winds blowing across the high summits can create snowy overhangs -- cornices,
冬天时，吹过高耸山顶的风会产生凸出悬崖的积雪，悬雪，
up to ten metres thick and weighing many tonnes.
厚达十米而且可达到数吨重。
In the spring, as the temperatures rise, the cornices may become unstable.
到了春天，当温度上升，悬雪可能变得不稳定。

And that can be catastrophic. Avalanche.
而那可能造成灾难。雪崩。
As it tumbles downwards, it accelerates to speeds of 100mph or more.
当雪翻滚下山坡，雪会加速到达时速100英里或更高。
Only a racer drone camera can follow its course.
只有竞速无人机能追上雪崩的轨迹。
In just two minutes, up to a million tonnes of snow hurtle down the mountainside.
在仅仅两分钟内，多达一百万吨的雪从山坡落下。
Avalanches can be hugely destructive, and climate change is making them more and more unpredictable.
雪崩非常具有毁灭性，而气候变化让它们越来越不可预测。