PINATUBO MATERIALIZED FROM A CLEARING MORNING MIST—a row of distant, friendly-looking green hills. "Doesn't look like a volcano at all, right?" said Newhall as we drove around it in a rented jeep. We were on our way to camp out in the crater, which has become a tourist site in the past seven years or so, after the lake grew to a half-mile across and returning trees and plants started drawing hikers.

Closer in, under a blistering sun, we rolled up a vast, barren, and roadless valley still covered with chalky deposits of ash and rock. Here and there, people were gathering golf-ball-size, 1991-vintage volcanic-pumice chunks for sale to manufacturers of stone-washed jeans.

Eventually the valley narrowed to a tortuous canyon, and we started walking. A gushing creek ran through jumbled piles of volcanic boulders and sand. A couple of hours later, we climbed through a fern-shaded defile and emerged onto a one-acre ledge. This overlooked the caldera—a vast bowl hemmed in by cliffs topped by jagged pinnacles. Far below, a deep-turquoise lake shimmered under a breeze.

There were voices. Three dozen people had set up a tent camp and unfurled a banner: PINATUBO 2006—ONLY THE BRAVE AND THE DARING SURVIVE. They were mostly Chinese-Filipino doctors and nurses on a weekend trip. Newhall was dumbfounded. "I knew there were tourists," he said. "But not like this."

A friendly young doctor walked over. "Good afternoon," he said in excellent English. "Your first time at Pinatubo?" Newhall just smiled.

After pitching our tent, we clambered down a few hundred feet to a small beach along the lake. "Sixteen years ago, where we are now, there were 1,000 meters of rock over our heads, and the temperature was about 300 degrees Celsius," he said. "Geology is supposed to move very slowly. But, you see, geology can move very fast."

He suggested a swim. We pushed off, and found the water pleasantly cool. We stuck to the edges, backstroking or crawling slowly along the sheer walls. About half a mile on, we rounded a bend and heard something like a large soup cauldron at work. From small holes in the cliff, boiling water and a faint sulfur smell were spurting—the result, he said, of circulation from some still-cooling rock below.

"It's just the volcano's way of saying, ‘I'm still here!' Now, don't get too close. It will cook you." A few minutes later I stupidly touched a hot rock with my foot, and yelped. Newhall winced. I backed off, and we basked together in the diluted heat plume 50 feet off. "Ah, it's good to be back here," he said with a sigh.

Back at the campsite that night, opaque clouds covered the sky. It was pitch black. The hiking club invited us to their campfire—a Coleman lantern—and one 30-ish doctor produced
a bottle of Fundador brandy. A tin cup was passed around, and we took turns chugging shots in a popular Filipino custom known as tagay.

When the group found out Newhall was a volcanologist, they could not ask enough questions. Sitting cross-legged on the ground, he told them that, these days, PHIVOLCS kept just one seismometer on Pinatubo. Lately it had picked up a few quakes, but small ones. The magma was probably three or five miles below and not going anywhere. The tin cup kept going around.

After a while, one doctor asked what everyone was wondering: "What are the chances of something happening to us tonight?"

Newhall said nothing for a moment, "Well , to make a random calculation the volcano erupts every thousand years, and it just erupted," he said "But we're only here tonight, right? So let's divide that by 365. what's that? About three in a million? Of course, that's for something big. For somthing samll , the chance is greater, but I can't say how much greater. It wouldn't have to very big. Sitting where we are, just a little burp would get us".

The circle fell silent. A bit of wind far above suddenly swept the clouds away. We were now under a great dome of brilliant stars, reflected in the lake.

"Well, in this world, nothing has a zero chance," Newhall finally said. "But whatever the chances are, they are vanishingly small. We should all sleep easy tonight."

Eventually everyone stumbled off to bed, and we did