Spring Basin W.A. over 2/3 of Oregon is built up from massive and multiple volcanic flows of lava and build up of ash, accumulating in places to several thousand feet thick. Much of it is ‘capped’ with basalts and rhyolite. Here on top of Horse Mountain a single dead Sagebrush, probably Artemesia arbuscula, stands next to an outcropping with our less common Hedghog Cactus, Pediocactus simpsonii ssp. nigrispinus.