The Uinkaret Volcanic Field, a 600 square-mile complex of cinder cones and basalt flows, extends about 50 miles north of the canyon rim. The age of the Uinkaret volcanic activity ranges from about 1.2 million years to as recent as 1,300 years. The Little Springs lava flow produced a cosmogenic helium age of 1,300 +/- years B.P. and pottery sherds dated at between 1,050 and 1,200 AD were found with the lava flow. Vulcan's Throne is a prominent 73,000 year-old cinder cone that is perched on the north rim of the canyon. Pleistocene lava flows repeatedly flowed down Toroweap Valley and several adjacent valleys into the Grand Canyon (see the image above for an example), at times forming large lava dams. At least twice in the last 160,000 yrs, the lava dams failed catastrophically and distributed flood deposits up to 30 miles downstream.

The Lava Falls Trail is the shortest route (about 1.5 miles and 2,500 vertical feet from the trailhead) to the Colorado River from the North Rim of the Grand Canyon. The trail is exposed and very steep and is seriously hot during the summer months - the hiker's log that used to be found at the trailhead read like a testament to just how unexpectedly difficult (and occasionally fatal) this ascent/descent can be. If you attempt it, bring more water than you think you'll need! The road to the trailhead is a bit sketchy on the last part and a high-clearance 4WD is recommended.