Wednesday, August 17, 2016
Ashfall Fossil Beds State Historical Park
One place we've wanted to visit for a long time is Ashfall Fossil Beds State Historical Park in north-east Nebraska. Staying in the campground at Niobrara State Park at the confluence of the Missouri and Niobrara Rivers, we were close enough for a day trip to visit the fossil beds.
Nearly 12 million years ago a huge volcanic eruption in southern Idaho sent a vast cloud of fine volcanic ash over a large part of North America. Around a seasonal pond, many animals died from respiratory failure caused by clouds of fine volcanic glass particles that settled in the depression the pond was located in. The smallest animals were the first to die and so were found at the bottom of the pond. The largest animals, such as the rhinos, may have lived as much as a month before they had all died. There is evidence of some scavenging of the remains, but mostly they were buried in ash and a later deposit of sandstone sealed the fossil bed until recently uncovered by erosion.
In 1971, a paleontologist doing geologic mapping happened upon a skull partly exposed on a hillside, which turned out to be that of a baby rhino. Field work in 1978 and 1979 uncovered an amazing assemblage of wonderfully preserved animal fossils, including birds, turtles, deer, horses, camels, rhinos and giant tortoises. The deposit is now mostly covered by a large shelter called the "Hubbard Rhino Barn" where paleontologists continue to unearth fossils.
Inside the Hubbard Rhino Barn