Why early geologists may have begun to suspect that the Earth was older than 6,000 years is because of the way the canyons formed When a you see a canyon there are layers that are inside. By looking at the layers you can tell how old the canyon is. The farther you dig in the canyon is the farther back you go in time. That is were fossils start to happen. When paleontologist digs into the canyon's layers they will find fossils. That is how they know how old dinosaurs are.