Camera travels 150 million years back in time as it tilts down the exposed sedimentary layers that make up sandstone cliffs in Zion Canyon, Utah. Visible here are nine distinct layers which are part of the Southwest磗 Grand Staircase, an immense sequence of sedimentary rock layers that stretches 200 kilometres from Bryce Canyon to the Grand Canyon. The layers were laid down when this area was covered by a vast inland sea. They were then thrust upward by the forces of plate tectonics and carved by erosion. Famous for its spectacular scenery, the 24 kilometre_long valley attracts more than three million visitors from throughout the world each year.