Just past Tuckup Canyon, at mile 165, the south edge of the Colorado River forms the boundary of the Hualapai Reservation. A few miles downstream on the right, 3,000-foot high cliffs loom above the river. On top is Toroweap, a remote overlook on the North Rim’s western reaches.

Below, at mile 179, is Lava Falls. Some consider these falls, a class 10 rapids, the fiercest white water in Grand Canyon.

The Colorado River drops 37 feet in just a couple of hundred yards. In 1869, John Wesley Powell’s men chose to make an arduous three-hour portage, rather than risk their wooden boats and remaining food stores against the churning rapids.

Powell recognized the signs of past volcanic activity along this section of the river. Upriver from the rapids, a volcanic neck, the black monolith Vulcans Forge, juts out of the water. Downriver, cascades of basalt rock mark the canyon walls, the flow of a volcano that erupted 1.2 million years ago. The flows created a dam about 1,400 feet high. An even higher dam formed near Prospect Canyon, creating a lake that extended all the way to present-day Moab. Over time, the sediment-laden Colorado River ground its way through these natural dams.

Lava flows are also evident at Whitmore Wash, at mile 188. The canyon walls are lower here, and the trail that leads up to the rim is less than a mile long, the shortest rim-to-river route in Grand Canyon. (The [node:49708 link Lava Falls Trail, at 1.5 miles, is the shortest entirely within the bounds of the park.) Because of its proximity to the rim, some outfitters use the beach at Whitmore Wash as a passenger-exchange point. The Bar-10, a family-operated ranch, offers lodging and an airstrip on the north side of the canyon, and on the south side, the Hualapai tribe operates a helipad.