A short history of nearly everything - Bill Bryson [115]
Hydrothermal explosions are also a significant risk. They can happen anytime, pretty much anywhere, and without any predictability. “You know, by design we funnel visitors into thermal basins,” Doss told me after we had watched Old Faithful blow. “It's what they come to see. Did you know there are more geysers and hot springs at Yellowstone than in all the rest of the world combined?”
“I didn't know that.”
He nodded. “Ten thousand of them, and nobody knows when a new vent might open.” We drove to a place called Duck Lake, a body of water a couple of hundred yards across. “It looks completely innocuous,” he said. “It's just a big pond. But this big hole didn't used to be here. At some time in the last fifteen thousand years this blew in a really big way. You'd have had several tens of millions of tons of earth and rock and superheated water blowing out at hypersonic speeds. You can imagine what it would be like if this happened under, say, the parking lot at Old Faithful or one of the visitors' centers.” He made an unhappy face.
“Would there be any warning?”
“Probably not. The last significant explosion in the park was at a place called Pork Chop Geyser in 1989. That left a crater about five meters across—not huge by any means, but big enough if you happened to be standing there at the time. Fortunately, nobody was around so nobody was hurt, but that happened without warning. In the very ancient past there have been explosions that have made holes a mile across. And nobody can tell you where or when that might happen again. You just have to hope that you're not standing there when it does.”
Big rockfalls are also a danger. There was a big one at Gardiner Canyon in 1999, but again fortunately no one was hurt. Late in the afternoon, Doss and I stopped at a place where there was a rock overhang poised above a busy park road. Cracks were clearly visible. “It could go at any time,” Doss said thoughtfully.
“You're kidding,” I said. There wasn't a moment when there weren't two cars passing beneath it, all filled with, in the most literal sense, happy campers.
“Oh, it's not likely,” he added. “I'm just saying it could. Equally it could stay like that for decades. There's just no telling. People have to accept that there is risk in coming here. That's all there is to it.”
As we walked back to his vehicle to head back to Mammoth Hot Springs, Doss added: “But the thing is, most of the time bad things don't happen. Rocks don't fall. Earthquakes don't occur. New vents don't suddenly open up. For all the instability, it's mostly remarkably and amazingly tranquil.”
“Like Earth itself,” I remarked.
“Precisely,” he agreed.
The risks at Yellowstone apply to park employees as much as to visitors. Doss got a horrific sense of that in his first week on the job five years earlier. Late one night, three young summer employees engaged in an illicit activity known as “hot-potting”—swimming or basking in warm pools. Though the park, for obvious reasons, doesn't publicize it, not all the pools in Yellowstone are dangerously hot. Some are extremely agreeable to lie in, and it was the habit of some of the summer employees to have a dip late at night even though it was against the rules to do so. Foolishly the threesome had failed to take a flashlight, which was extremely dangerous because much of the soil around the warm pools is crusty and thin and one can easily fall through into a scalding vent below. In any case, as they made their way back to their dorm, they came across a stream that they had had to leap over earlier. They backed up a few paces, linked arms and, on the count of three, took a running jump. In fact, it wasn't the stream at all. It was a boiling pool. In the dark they had lost their