Day 19 (June 2). The Ashfall Fossil Beds of Nebraska

From: Lincoln, NE

To: Winner, SD

Miles today: 330

Total miles: 4597

Nebraska, at least eastern Nebraska, is a lot hillier than I expected.  I would call it hillier than the Flint Hills, and it got progressively more hilly as I moved north toward South Dakota.  There were certainly lots of large farms, but there was plenty of pastureland as well.  I tried to stick to smaller roads; I started with US 34 west out of Lincoln, then NE 15 north over the braided Platte River, then west on US 275 to Norfolk, then NE 13 northwest (diagonal!) to US 20, and then finally north on a small road to one of my prime destinations on this trip: Ashfall Fossil Beds State Historical Park. 

About 12 million years ago (the Miocene, for those keeping score), the supervolcano that currently resides under Yellowstone National Park in Wyoming blew, spreading significantly more ash than Krakatoa did in 1883, which led to the “year without a summer” in many regions.  (At the time, the hotspot was actually under Idaho; plate tectonics and all that.)  This grey blizzard blew across what is now central region of the US (see the map), depositing an average of about 6 inches of ash in eastern Nebraska. 

Display of the ash fallout from the Miocene eruption in Idaho.  The Ashfall site is identified in yellow letters.

Living in eastern Nebraska at this time were five different species of horses, a number of camel species, and, interestingly, rhinos.  At one particular spot was a water hole about 10 feet deep, and maybe 100 meters across.  The cloud came in, and then wind blew the stuff around like snow for weeks. The animals breathed this stuff; it is essentially microscopic shards of glass that get embedded in your lungs.  The dying took an extended period (as is evidenced by the way the fossils are stacked on top of each other).  Six inches of ash is not enough to bury large animals, but – and this is the key geological feature – lots of animals hung around the waterhole during this period, and were eventually buried in it.  The wind kept blowing the ash and eventually filled in the waterhole, entombing hundreds of carcasses.  Since the rhinos are on top, it is assumed that they died last.  Their skeletons are amazingly preserved.  Here are a couple of shots.  Ten million years later, after some other periods of deposition and then erosion, humans stumbled across the site.  It met all of my expectations.

Scenes from the Rhino Barn

Amazingly complete 3-toed horse

The morning had been chilly again; overcast and in the mid 50’s.  By the afternoon it cleared up and warmed up.  Also, the wind picked up. I didn’t really think about the gusts of wind I would be facing when I planned this, but I was wrestling with the bike all afternoon. 

From Ashfall I resumed by trek west on US 20, then north on US 281 out of Nebraska and into South Dakota.  (South Dakota is one of three states – now two – that I had not been to.)  I am in the town of Winner tonight, and tomorrow I hope to go further west and view the badlands, if the weather permits.  One final note on this subject: in a lot of public places where there is a TV, it is often set to CNN if not sports.  Here they all seem to be set to the Weather Channel.  I find myself paying a lot more attention to it than I do to CNN.