Watch Crash Course Geography Season 1 Episode 19 Online

Today we're going to tell the story of a quiet revolution in the 1960s that shifted our entire understanding of how the Earth works. We currently believe that the Earth's broken outer shell rises from the mantle and folds back in - kind of like a dance of creative destruction and reconstruction - giving us our continents and oceans, mountains and valleys, volcanoes, and earthquakes. And it would take a group of scientists all over the world to get us this grand unifying theory of plate tectonics.