Updated: May 7, 2019
The earth’s crust is about 50 miles thick, and made of moving plates. Earthquakes happen when the plates separate, collide, or rub against each other (many famous plates have ruined their careers this way). Earthquakes cause about 10,000 deaths every year – usually in the form of traffic accidents caused by people posting about the quake on social media. When tremors happen deep inside the earth, there’s usually no ill-effect. However, they can be very dangerous close to the surface. It works much like indigestion: it’s not a problem until it’s visible. The first waves are called primary waves or P-waves (P stands for pfirst). There are several other lettered waves that follow, but pretentious critics roll their eyes at these, claiming that the original was better. In 1989, the World Series was interrupted by a 7.1 magnitude earthquake that caused a 10-day delay in the game, which the audience didn’t notice.