Gibbon Falls plunges eighty-four feet, then tumbles toward the Yellowstone Caldera about one-quarter mile downriver. As the falls erode the rock below, the waterfall grows higher and migrates farther from the caldera’s rim. The surrounding landscape reflects Yellowstone’s volcanic and glacial history: about 640,000 years ago, an eruption of the Yellowstone volcano hurled vast amounts of ash that intense heat welded into Lava Creek tuff. The Gibbon River flows through a canyon of this tuff, which also forms the hillsides above the river, while nearby exposures include rocks deposited by the Yellowstone ice cap around fourteen thousand to sixteen thousand years ago. Although the caldera itself is not clearly visible, later eruptions sent underground magma through cracks, spreading lava across the surface; over millennia, these lava flows partly filled the caldera and created the present landscape. Traveling south leads into the caldera, while traveling north leads away from it.