Mount Gould and Angel Wing, Glacier National Park, Montana. 2002

This is the post card view from the Many Glacier Hotel area. The dark horizontal band of igneous rock ( Purcell Sill ) on Mt. Gould is diorite. 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. Since the sill was injected after the sedimentary layers were deposited, geologists can’t simply say the layers above it are younger than it and those below are older than the sill. Nonetheless, when geologists see it they know they are looking at the Helena (Siyeh) Formation, which lies just above the older rocks of the Empire Formation, and just below the younger rocks of the Snowslip Formation.Height of Mount Gould is 9550 ft. The only through road, Going to the Sun Road is normally plowed by end of June and is on the other side of Gould on the Continental Divide.