Rivers of Rock The Hidden Science and Story of Glaciers

Geologists classify a glacier as a rock. It is a persistent body of natural ice, made of crystals the way granite is made of grains, and it is constantly moving under its own weight. That small piece of classification changes how you look at one. A glacier is a kind of rock that has learned to flow: a river that happens to move a few meters a year, or a few centimeters a day.

Most of us meet glaciers as postcards: white, silent, apparently frozen in time. But that stillness is an illusion of scale. Watch a glacier for an afternoon and nothing seems to happen. Watch it for a decade and you see a conveyor belt carrying stone, sediment, and snow from high mountains toward the sea. Watch it for a hundred thousand years and you see a force that has shaped the landscapes where much of humanity lives.

This episode follows glaciers through four chapters. First, the physics that makes ice move. Second, the people who worked out what glaciers had done to the Earth, and the strange fact that they store ancient air. Third, the water they supply to billions of people. And finally, what happens to a culture, and to a planet, when the ice begins to disappear.