Since part of the focus of Trip 4 is on geology, Zion and Bryce Canyon are appropriate stops. They are part of the Grand Staircase, the most extensive record of geologic history on earth. The various layers of sedimentary rock at Bryce and Zion show a continuity that continues into the Grand Canyon. For instance, the lowest layer of rock in Zion, the Kaibab Formation, makes up the topmost layer of the Grand Canyon. This is a great way to experience the continuity of sedimentary layers over many miles (80 miles from Zion to the Grand Canyon).