A short history of nearly everything - Bill Bryson [102]
“It was a dumb place to look for bones,” he said happily. “But I wasn't looking for bones. I was thinking of making a geological map of eastern Nebraska at the time, and really just kind of poking around. If I hadn't gone up this ravine or the rains hadn't just washed out that skull, I'd have walked on by and this would never have been found.” He indicated a roofed enclosure nearby, which had become the main excavation site. Some two hundred animals had been found lying together in a jumble.
I asked him in what way it was a dumb place to hunt for bones. “Well, if you're looking for bones, you really need exposed rock. That's why most paleontology is done in hot, dry places. It's not that there are more bones there. It's just that you have some chance of spotting them. In a setting like this”—he made a sweeping gesture across the vast and unvarying prairie—“you wouldn't know where to begin. There could be really magnificent stuff out there, but there's no surface clues to show you where to start looking.”
At first they thought the animals were buried alive, and Voorhies stated as much in a National Geographic article in 1981. “The article called the site a ‘Pompeii of prehistoric animals,' ” he told me, “which was unfortunate because just afterward we realized that the animals hadn't died suddenly at all. They were all suffering from something called hypertrophic pulmonary osteodystrophy, which is what you would get if you were breathing a lot of abrasive ash—and they must have been breathing a lot of it because the ash was feet thick for hundreds of miles.” He picked up a chunk of grayish, claylike dirt and crumbled it into my hand. It was powdery but slightly gritty. “Nasty stuff to have to breathe,” he went on, “because it's very fine but also quite sharp. So anyway they came here to this watering hole, presumably seeking relief, and died in some misery. The ash would have ruined everything. It would have buried all the grass and coated every leaf and turned the water into an undrinkable gray sludge. It couldn't have been very agreeable at all.”
The BBC documentary had suggested that the existence of so much ash in Nebraska was a surprise. In fact, Nebraska's huge ash deposits had been known about for a long time. For almost a century they had been mined to make household cleaning powders like Comet and Ajax. But curiously no one had ever thought to wonder where all the ash came from.
“I'm a little embarrassed to tell you,” Voorhies said, smiling briefly, “that the first I thought about it was when an editor at the National Geographic asked me the source of all the ash and I had to confess that I didn't know. Nobody knew.”
Voorhies sent samples to colleagues all over the western United States asking if there was anything about it that they recognized. Several months later a geologist named Bill Bonnichsen from the Idaho Geological Survey got in touch and told him that the ash matched a volcanic deposit from a place called Bruneau-Jarbidge in southwest Idaho. The event that killed the plains animals of Nebraska was a volcanic explosion on a scale previously unimagined—but big enough to leave an ash layer ten feet deep almost a thousand miles away in eastern Nebraska. It turned out that under the western United States there was a huge cauldron of magma, a colossal volcanic hot spot, which erupted cataclysmically every 600,000 years or so. The last such eruption was just over 600,000 years ago. The hot spot is still there. These days we call it Yellowstone National Park.
We know amazingly little about what happens beneath our feet. It is fairly remarkable to think that Ford has been building cars and baseball has been playing World Series for longer than we have