This photo, taken from an
airplane on my trip to Nevada in
June, 2007, shows the Grand
Canyon. Several geological
processes helped form the canyon,
including erosion by the Colorado
River which flows through it.

Remember when we studied plate
tectonics? This photo shows two
plates as they collide and build
a mountain. The darker plate at
the rear is slipping over the
lighter-colored plate in front.
(Taken at Valley of Fire, Nevada,
06-22-07.)