Corey Johnson (Narrator), Shelton Johnson (Self - Park Ranger, Yosemite National Park Service), Bryan Law (Self - Geologist, University of Nevada, Reno), Allen Glazner (Self - Geologist, University of North Carolina), Greg Stock (Park Ranger, Yosemite National Park Service / Self - Geologist), Bob Anderson (Self - Geologist, University of Colorado at Boulder), Scott Gediman (Self - Park Ranger, Yosemite National Park Service), Valerie Zimmer (Self - Geological Engineer, Univ. of California), Jonathan Keeble (Self - Narrator)