There are multiple explanations for the origin of Unaweep Canyon. In the late 19th century, members of the Hayden Survey recognized the oddity of a canyon with two outlets, and suggested it was carved by the ancestral Colorado or Gunnison river. Many others have also suggested it was carved by either the Gunnison or Colorado Rivers, but evidence for gravel deposits characteristic of these rivers was elusive, and the existence of the divide remains difficult to explain. Several have suggested that Plio-Pleistocene uplift caused diversion of the (Colorado and/or Gunnison) river(s) and abandonment of the canyon. But rates of river incision typically exceed those of tectonic uplift, making this unlikely. The many apparent glacial-like features of the canyon's inner gorge have led some to suggest a Pleistocene glacial origin for the canyon, but the low elevation of the canyon, and lack of Pleistocene glacial deposits, make this problematic.