Over 1.25 million years ago, a massive volcanic eruption created a 13-mile wide dimple in northern New Mexico. Hot springs, fumaroles and Redondo Peak, a 11,00-foot tall lava dome, reveal the caldera’s geologic past. Most of the area is now part of Valles Caldera National Preserve. Native Americans in the area used volcanic obsidian for arrowheads and spear points, starting a hunting tradition that lives on in the park today. Photo by Andrew Gordon (www.sharetheexperience.org).