Lava Dam and Diversion
Approximately 150,000 years ago, the eruption of Merriam Crater, a small cinder cone volcano, produced a lava flow that traveled seven miles to this point and cascaded 200 feet down into the Little Colorado River Gorge. The river was then forced to create a new course, bending around the lava flow and then dropping back into its original channel, forming Grand Falls. Grand Falls typically flows in response to snowmelt in the spring and heavy thunderstorms during the monsoon season of late summer. Today, the river continues to downcut and erode into its original channel on its way to the Colorado River in the Grand Canyon.