Grand Falls, in the Painted Desert on the Navajo Nation about 30 miles northeast of Flagstaff, is a natural waterfall system also called Chocolate Falls for the Little Colorado River’s muddy-brown color. Fed by snowmelt and seasonal rain, its flow can range from a roaring surge after storms or spring runoff to a trickle or complete stop in dry periods, and that muddy water is a major source of the river’s opacity. The falls formed when lava from nearby Merriam Crater dammed the river, forcing it to reroute and creating a waterfall where it later rejoined its original course. Remote and hard to reach, the site has been closed since March 2023 for environmental safety.