Mount Moran reflects the geologic forces shaping the Teton Range. It was formed of a massive block of metamorphic gneiss, cut by dikes of igneous granite and diabase, capped by sedimentary sandstone, and flanked by glaciers, and this formidable peak dominates the park’s northern skyline. The gneiss and granite are among the oldest rocks in North America, 2.7 and 2.5 billion years old respectively. These resistant rocks form the core of the Teton Range. The vertical Black Dike of 775 million year old diabase is about 150 feet wide and juts from the mountain’s face because the surrounding gneiss has eroded away.