The idea of plate tectonics is the cornerstone of modern geology.

But it wasn't always that way, and it wasn't an easy idea to sell. Today, we'll meet two scientists who faced ridicule for proposing continental drift: a German climatologist and an American cartographer, the greatest of her generation. We'll also meet a lost expedition to Greenland, the Mid-Atlantic Ridge, and Jacques Cousteau.

Extra credit: Look at maps of the ocean floor, or try to align the continents in various patterns on a map.