By the third day of our adventure, we finally made our way to Black Canyon of the Gunnison National Park, featuring some of the steepest cliffs, oldest rock, and craggiest spires in North America. Our hikes along the rim were limited to the distance from our truck to the overlooks, but the spectacular views were inspiring nonetheless. Notice that the south rim (to the right) has eroded back father than the north rim (to the left). The south rim faces north, so it does not receive as much sun and does not dry out as quickly as the north rim. Because moisture is an important factor in erosion, a moist slope tends to erode faster than a dry slope.

Another spectacular feature of the canyon is the pinkish pegmatite dikes that form bands across Painted Wall, the tallest sheer cliff in Colorado. For millions of years the Gunnison river has been eroding the deep, narrow gorge through the precambrian rocks of the Gunnison Uplift, a dome of mostly dark metamorphic gneisses and schist. The pegmatite veins were originally molten rock, or magma, which squeezed, or intruded, into fissures withing the already-hardened gneisses and schist deep within the earth. In some places the pegmatite, a granite more resistant to erosion than the surrounding rock, shows up in vertical fins; in others it manifests as serpentine bands that pattern the darker rock, as on the Painted Wall.

Our excursion left us tired and hungry, so we ended out day with ribeye steak and veggies grilled to perfection, and a viewing of An Intimate Evening with David Foster on the local PBS station. It was followed by ABBA Forever, A Celebration, an unexpected surprise that kept us watching even though we had intended to go on a stargazing stroll.