The Uinkaret volcanic field straddling the Grand Canyon contains cinder cones that have produced lava flows that repeatedly cascaded into the Grand Canyon, forming temporary lava dams up to 200 m high. Two of the most prominent landmarks are Vulcan's Throne, a cinder cone on the north rim, and Vulcan's Forge, a small volcanic neck erupted within the Colorado River, 1000 m below. Most of the Uinkaret field lies north of the Grand Canyon on the Uinkaret Plateau between the Toroweap and Hurricane faults. The Uinkaret volcanic field is largely Pleistocene in age, and Vulcan's Throne has a cosmogenic helium age of about 73,000 years. Volcanic activity has continued into the Holocene. One lava flow, from Little Springs, south of Pliocene Mount Trumbull, has a cosmogenic helium age of 1300 +/- 500 years BP. Pottery sherds dated at between 1050 and 1200 AD were found within the Little Springs lava flow, which occurred about the same time as the Sunset Crater eruption in the San Francisco volcanic field to the SE.