can't help but take lots of pictures as we make our way up the switchbacks. This is looking to the SW. We will be up on that saddle over there in less than a couple hours. Oh, you can see part of the "Purcell Sill" (now referred to as the "magmatic sill"); The black and white stripe

Sills are formed when magma forces its way in between layers of sedimentary rock and then hardens. Throughout most of the park, the sill stands out as a 130 to 300 ft. dark layer of diorite sandwiched between strips of white, low-grade marble that formed as heat from the cooling magma baked the limestone. This heat also drove out organic material, bleaching the rock and causing more contrast between the darker diorite and the marble