(Francisco Kjolseth | The Salt Lake Tribune) Cari Johnson, a geology professor at the University of Utah and Jack Schmidt, a professor at Utah State University’s Center for Colorado River Studies analyze the so-called Dominy Formation in Waterhole Canyon, one of the tributaries of the Colorado River in Cataract Canyon. The mountains of sediment illustrate the high water mark once reached by Lake Powell before its retreat as flooding events slowly carve away at the sediment.