Ashfall slideshow

Wide view of the Hubbard Rhino Barn interior, with dozens of fossil skeletons exposed in pale volcanic ash and marked by red numbered discs.

Various animal skeletons, most prominent of which are prehistoric rhinos, are labeled for easy visitor verification within the Hubbard Rhino Barn and Ashfall Fossil Beds State Historical Park outside of Royal, Neb.

Four people gathered around 3D scanning equipment on the ash floor of the rhino barn, beneath signs reading “The Dead Zone” and “The Skeleton Zone.”

A team of staff, researchers and interns use 3D scanning software to preserve the paw prints of a “bone crushing dog” left in the ash deposit. They include, from left: Rick Otto, retired superintendent of Ashfall Fossil Beds; Shane Tucker, highway paleontologist with the Nebraska State Museum; Jennifer Lee, senior, Nebraska State Museum intern; Rowan Hulpke, senior, Ashfall Fossil Beds intern.

Sam Matson smiling as he holds a small, slender excavation tool toward the camera inside the Ashfall Fossil Beds visitor area.

Sam Matson, superintendent of Ashfall Fossil Beds State Historical Park, displays one of the many, tiny, tools researchers use to undercover fossils within the layers of ash inside the barn.

Sam Matson crouching on the pale ash surface of the rhino barn, tapping it with a small hand tool.

Sam Matson, superintendent of Ashfall Fossil Beds State Historical Park, taps on the surface of the ash layer. Due to presence of microscopic air bubbles throughout the ash layer, tapping on said layer produces a different sound than tapping on the rock below. This helps researchers and interns determine when they’ve reached the bottom.

Rowan Hulpke bent over a large fossil bone supported in a foam cradle, scraping glue from a crevice with a fine dental pick.

Intern Rowan Hulpke of Fort Collins, Colo., scrapes away at glue in the crevice of a large bone at the lab at Ashfall Fossil Beds State Historical Park. Hulpke, spending her summer in Royal, is a senior studying geology at Macalester College in Minnesota.

A hand holding five small excavation tools: a slender blade, a stiff-bristled paint brush and three dental picks.

Small tools like these pictured, including stiff paint brushes and dental picks, are used to gently scrape away at the ash layers covering fossils inside the Hubbard Rhino Barn.

Small canine paw prints preserved in a pale ash surface, marked with numbered tags, black direction arrows and red-and-white scale bars.

Small dog tracks, like those pictured, were left behind in an ancient algae layer around the same time the watering hole was being slowly covered by ash. Skeletons from the bone crushing dogs responsible for these tracks have yet to be found in the area.