San Andreas Is a Crock

But there’s a reason West Coast geologists are fixated on the “big one.”

We don’t need to tell you the new San Andreas movie is absurd. But as with most B movies, it does piggyback on real-life fears—and you won’t find many people from the West Coast who aren’t familiar with the concept of the “big one.”

As the video above explains, California has hundreds of major fault lines beneath its surface—the 810-mile San Andreas is simply the most notorious—and the U.S. Geological Survey says it’s near certain there will be a big earthquake there in the next 30 years. The question is how big.