Inside the Visitor's Center

NARRATOR: Giraffe camels no longer roam North America. Neither do barrel-bodied rhinos. But ten million years ago these exotic big game animals were natives of North America, and the Great Plains was a tropical savanna.

MIKE VOORHIES: Well, I think most people's idea of Nebraska is sort of dullsville. I mean,  like corn fields, maybe the interstate highway, and not much else. But if you scratch the surface literally anywhere in the state, you are likely to find the remains of these prehistoric big game animals.

(BULLDOZER ENGINE)

NARRATOR: In this case scratching the surface requires a bulldozer. Mike and a crew from the Nebraska State Museum are continuing an excavation at a fossil bed that Mike first discovered in 1971. He named it Ashfall Fossil Beds.

MIKE VOORHIES: I'm more accustomed to working with this stuff by the teaspoonful. So when I see somebody moving it by the houseful, I get a little, little apprehensive.

NARRATOR: Without the bulldozer this work would take Mike and his crew an entire summer. Now it will take only hours to scrape off eight to ten feet of dirt to expose the top of the fossil bed, but the dozer is plowing off  more than dirt. It's stripping away millions of years of the planet's history. In search of a special slice in time. In a special type of deposit, volcanic ash.

MIKE VOORHIES: Well we certainly don't associate Nebraska with volcanoes. In fact as far as we know, there never have been any volcanoes in Nebraska, but Nebraska does have a tremendous amount of volcanic ash in it. We have been downwind from volcanoes in the Rocky Mountains for many, many millions of years.  And the Ashfall ash is just one of literally dozens of ash beds that have been spread out across the plains.

(EXPLOSION)

MIKE VOORHIES: Mount St. Helens was a pretty awesome explosion. Large numbers of animals and a few people were killed on the slopes of the mountain. But in context of this volcanic ash bed that we have here in Nebraska, Mount St. Helens was no more than a little puff ball.

NARRATOR: When Mount St. Helens erupted it poured thousands of tons of ash across the nearby countryside. But by the time the volcanic cloud drifted two hundred miles away, it deposited barely an inch of ash. But when the ancient volcano's cloud reached Nebraska, it left an ashbed one to two feet thick over thousands of square miles, and in places like the Ashfall water hole, it drifted to depths of up to ten feet.

MIKE VOORHIES: We're almost certain it came from southwestern Idaho, where there is an enormous, ancient volcanic center that's ten million years old. And it has the right chemistry. Each kind of volcanic ash has a slightly different amount of iron, and uranium, and other chemical constituents. And this particular volcanic ash at Ashfall matches up very well with this volcanic center in southwestern Idaho, which is about a thousand
miles due west of here. So that was a truly tremendous eruption.

MIKE VOORHIES: And I've looked at enough of this material under the microscope to be a afraid of it, because it looks like a bunch of little knives. Volcanic ash is, uh, shattered glass, that's really what it is.

(MUSIC & ANIMAL SOUNDS)

NARRATOR: The tragedy at Ashfall began as clouds approached from the west, shadowing the area around the waterhole. The animals took little notice, even as the first flakes gently drifted down like newly falling snow, but it was not snow and it did not stop.

MIKE VOORHIES: What I envision happening is that the entire landscape here for literally thousands of miles around us was blanketed with a fall of very fine white powder. Just imagine yourself walking across a field of snow, except that instead of snow, you've got, say, a couple of feet of volcanic dust. Every time that you take a step, you raise a cloud of ash and you inhale the stuff.

(WIND, ANIMALS GROANING)