Off the Beaten Path: SuperVolcanos & America’s 12 Million-Year-Old Zoo

Most east-west travelers whiz along Interstates and miss the good stuff. U.S. Highway 20 about 100 miles west of Sioux City, Iowa takes you through the heart of America's corn and soybean super farms, but leads you to the Ashfall Fossil Beds in Nebraska. Millions of years ago herds of rhinos, horses, camels, elephants, and giant tortoises grazed there.

That is until a gigantic volcano in Idaho (over 900 miles away) blew a 50-mile wide hole in the ground, sending a vast cloud of toxic ash drifting across the great plains of the USA. The ash killed birds, and then many kinds of exotic Miocene era animals.  At Ashfall Fossil Beds, many animals gathered at a water hole as they slowly died from the effects of the volcano fallout.  The result is an incredibly high density of fossils in one place.  The birds and smaller animals died first, with the larger ones succumbing more slowly to lung disease.  The ash covered them, preserving their skeletons intact in the places they died.  Rhinos are the most common, with infants often dying next to their mothers.

In 1971 paleontologist Mike Voorhies found the intact skull and jaw of a baby rhinoceros, and with later investigation found its intact fossil skeleton. With funding from the National Geographic Society in the late 1970s dozens more complete skeletons of rhinos, horses, and birds were unearthed. Today you can see the remains of more than 100 complete rhinos and other animals uncovered where they fell and died and were preserved.

So many individual animals have been uncovered that a population analysis can be made, studying their environment, social and mating habits, and their predators. The climate of Nebraska was warmer 12 million years ago. Here three-toed horses and early one-toed horses evolved into ancestors of today's single-toed horses.

The site of the supervolcano was southwestern Idaho and the explosion was a thousand times more powerful than that of the 1980 Mount Saint Helens blast. This was the second of the major eruptions of the “hotspot” that include the Yellowstone caldera (the 6th eruption).  Although there are a number of hotspots in the world (the Hawaiian Islands being the best known), the hotspot that includes Yellowstone is the only one on land.  As the North American plate moves steadily westward the hot spot has moved across Nevada, Idaho and Wyoming. The Yellowstone caldera is one of the largest calderas in the world.

The visitor travels 7 miles north of U.S. Route 20 just west of the town of Royal. The State Historical Park collects a fee per person and an out-of-state one-day pass fee ($29 for 3 of us). There is a splendid museum with interpretive exhibits describing the geologic dating process and summary of events leading to the park's development.

The real deal are the open quarries where fossil bones are exposed in situ. Paths lead past viewpoints. In 2008 the Hubbard Rhino Barn, a 17,000 square-foot shelter, was constructed protecting a most impressive collection of partially excavated rhino and other animal skeletons.  There are display boards of all the types of extinct animals found and details about them.  Paleontology interns from various universities work all summer long at painstakingly revealing buried skeletons. You can talk to these workers and learn exactly what they are doing that day.

Roger met Dr. Mike Voorhies, now a professor emeritus, at a dig surface just outside the door of the barn. He used a forked trowel and a paint brush to uncover tiny bones of a bird from the white crystalline glass ash. He said, “What makes this site so unique is the abundance of animals, seeds of hardy grass, and paleoclimate evidence in one place. The variety of contemporaneous animals shows those that preyed on each other. And we see adult animals, youthful animals, and babies. We see evidence of animal diseases in some older adults, and battle scars.…The whole community and its environment is represented!”

It would be easy to spend all day at the Ashfall Fossil Beds State Historical Park in Nebraska because there is so much to see and learn. We were headed for Yellowstone and this stop gave us a new perspective on the Yellowstone Hotspot.  That's the advantage of off-the-beaten-path sites that those who travel only by airways and Interstates never experience.




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