Also in Grand Canyon news, there's a new theory of its formation just out which deems its age much greater than previous estimates. While the structure of its constituent rock strata is pretty simple, explaining the formation of the Canyon itself has long been very contentious. "If you ever want to see geologists screaming at each other," an informed person once told me, "ask them to interpret the Grand Wash Cliffs Formation." We'll see how the new theory holds up long-term.