Almost 50 million years ago, the biggest landslide in Earth's history occurred in Wyoming. An entire mountain slid 45 kilometers at one-third the speed of sound. But how could this happen when the slope was only 2 degrees?

Even if a volcano is just a few miles away, you might not hear it erupt. How is that possible? It has to do with a phenomenon known as sound shadows! Hank will tell you all about it in this new episode of SciShow! Join us!