Ice may be nothing more than frozen water but it holds extraordinary power. Descending 150m down a frozen waterfall, Dr Iain Stewart looks at a glacier in action from below and discovers why the huge Jacobshaven Glacier is retreating. He shows how ice shaped our past and may now threaten our future.

Originally released by BBC Worldwide Learning, 2007. Streaming video file encoded with permission for digital streaming by Infobase on November 21, 2019.