For three hours, a team of scientists collected samples from deep inside the crater of a seemingly peaceful volcano. Suddenly, an apocalyptic eruption shot white-hot rocks into the darkening sky. Nine people were killed high on the Colombian mountain that day, and volcanologist Stanley Williams barely escaped with his life. In an exclusive preview from the controversial new book Surviving Galeras, Williams recalls the horror.

By Stanley Williams and Fen Montaigne

Studio Hererra, Pasto

In harm's way: Galeras menaces the town of Pasto, August 1936.

MY COLLEAGUES came and went in the clouds. Banks of cumulus drifted across the peaks of the Andes, enveloping us in a cool fog that made it impossible to see anything but the gray rubble on which we stood. As morning gave way to afternoon, the clouds occasionally dispersed, offering a heartening glimpse of blue sky and revealing the barren, imposing landscape around us.

We were perched at 14,000 feet, on top of the Colombian volcano Galeras. It was January 14, 1993. At the center of the tableau was the volcano's cone and its steaming crater. Surrounding the cone on three sides were high walls of volcanic rock forming an amphitheater almost a mile and a half wide, a subtle palette of dun, gray, and beige. Occasionally I glimpsed in the west a forested, razorback ridge sloping toward the equatorial lowlands below—the flank of an ancient volcano, one of many vestiges of earlier Galerases, in various stages of decay.

Around 1 p.m., four other geologists and I, part of our larger party of 13 scientists, stood on the crater's lip and gazed inside. Some 900 feet wide and 200 feet deep, the mouth of Galeras was a misshapen hole strewn with jagged boulders. Sulfuric gases shot from fumaroles, or vents, with a hiss, assaulting the nostrils with acrid odors and further obscuring the landscape in a swirl of vapors. The gas clouds often veiled Igor Menyailov, a Russian volcanologist sitting amid a jumble of rocks and thrusting a glass tube

into a fumarole. The 55-year-old, who'd learned English by listening to black-market Elvis recordings, swiveled his head away from the vents as he talked with Colombian scientist Nestor García. Circling the rim of the crater, appearing and reappearing in the fog like a phantom, was English volcanologist Geoff Brown, accompanied by Colombian scientists Fernando Cuenca and Carlos Trujillo. Brown was taking the volcano's pulse with a highly sensitive device called a gravimeter. Like Igor, he was trying to determine if magma was on the move. We all used different methods, but our goal was the same—to forecast eruptions, to predict when Galeras might blow. We all wanted to save lives. Nine people would lose theirs that day.

This is what I remember. I know now what an elusive thing memory can be.