"Here are a few things to do on a highway trip: Play 20 Questions, plug your kids into some sort of electronic anodyne, lose your mind. Here's another idea: Look for gneisses and amphibolites; seek out scarps, klippes and fault slices. Head for the Silurian boundary. Instead of feeling miserable and confined, feel the bones of the earth as you ride past the exposed evidence of the planet's history. . . . That's roadside geology, road food for the mind and eye."