飞机跑道破裂

The biggest concern was that the ice airstrip might break apart,

but, luckily, it held and everyone was able to evacuate

when the weather improved. The Frozen Planet team's clearest demonstration

of the power and unpredictability of breaking ice came when they went to film the melting

of a frozen Canadian river. Producer Mark Linfield and

researcher Matt Swarbrick have travelled to the Far North of Canada.

Matt, when was the last time we saw a car? I don't know, about three hours ago.

They've driven through the vast Northwest Territory on a mission to film the moment when this frozen waterfall breaks apart.

The break-up, when the frozen river above the waterfall thaws and masses of water start to flow again,

can be a spectacular event. But predicting exactly when it's going to break