Tanner Graben is a prominent cliffside rock formation in Arizona’s Grand Canyon, just below the junction of the Little Colorado and Colorado rivers and opposite Tanner Canyon. At its base, Tanner Creek forms Tanner Rapid, linking the landform to a notable feature of this river corridor. Its most striking visual element is a dark middle band of Cardenas Basalt set against softer reddish rocks. The formation also exposes tilted units of the Grand Canyon Supergroup, including the Nankoweap Formation above and the Dox Formation below. Shaped by the Butte Fault and related larger structures, it vividly reveals the canyon’s tectonic and stratigraphic history.