Grand Canyon of the Yellowstone River from Artists Point by Ron Schott

Canon PowerShot SX10 IS

GigaPan Epic100 (1st generatio...

America's first National Park, Yellowstone, takes its name from rocks that were erupted following a cataclysmic volcanic eruption 640,000 years ago, subsequently hydrothermally altered, then exposed by the downcutting and erosion of the isonymous river. Lower Yellowstone Falls, seen here from Artists Point, is the very epitome of the ongoing geologic evolution of this remarkable landscape.

This GigaPan illustrates a host of geologic landforms and processes. Igneous processes are represented by the rhyolitic bedrock that forms the walls of this gorge, erupted in the aftermath of a caldera forming eruption 640,000 years ago. Subsequently these rocks were altered by the active hydrothermal system that even today transfers heat to the surface from a shallow and active magma chamber. The alteration has weakened these rocks and provided a path of comparatively little resistance for the Yellowstone River to carve this grand canyon. The canyon is a textbook example of a juvenile river valley with the classic V-shape in cross section where mass wasting events (for example the rock avalanche chutes at right) carry sediment down slopes that form at the angle of repose. Lower Yellowstone Falls marks the point where the river is actively carving through a more resistant layer into the softer rocks below - it's headward retreat continually lengthens this gorge. The rainbow in the mist at the base of the falls is a reminder that the sun's energy drives the hydrologic cycle which is locked here in a constant struggle with the rock cycle which uplifts and renews these mountains, fueled by Earth's internal heat rising up from below.