Fables tell us that it's really stupid to build a house on sand. In reality, you can build your house on sand—as long as you live in a tectonically stable part of the world. If you don't, an earthquake will turn the sand into quicksand, and as a consequence, it will turn your house into history.
The MinuteEarth video above uses the case of the Jamaican pirate haven city of Port Royal to explain liquefaction. In 1692, the city sank into the sea during an earthquake. Why? Because it was built on sand. Usually, sand behaves like a solid—even if it sinks a little bit when you stand on it, the sand particles quickly become compressed enough that they support your weight. The same applies to building structures. But when there's an earthquake, the particles vibrate so much that this structure all but disappears, turning sand into goopy quicksand—which is when you say goodbye to anything that was sitting on top of it. Makes you think twice about that beach front property.