Ashfall Fossil Beds in northeastern Nebraska preserves an unusually complete snapshot of a Miocene die-off caused when volcanic ash from the Bruneau-Jarbidge eruption drifted east across the Great Plains about 12 million years ago. At a watering hole, ash accumulated deeply enough that animals seeking relief inhaled it and died over time, leaving a sequence of deaths from smaller species to larger ones. The site is especially known for abundant Teleoceras, along with horses, camels, birds, and turtles. Many skeletons remained articulated and preserved in three dimensions, revealing scavenging, diet, and a warmer grassland-and-tree landscape. Discovered in 1971 by Michael Voorhies, the site remains an active excavation and research area.