To photograph Tessier in one of Mutnovsky's steaming craters, Peter grappled not only with stinging eyes and his own cumbersome gas mask but also with his gear. Sulfuric gases quickly corrode a camera's inner workings; changing film required both a protected place and a deft hand. Winds cleared the steam for just milliseconds, allowing Peter only an instant to capture the crater wall's brilliant sulfur deposits: "I was improvising all the time because the conditions were so difficult."

We hiked through soft ash, sinking knee-deep at times, climbed heaps of shattered rock, and scrambled in and out of ragged gorges. Through wind and whipping clouds we climbed to the crater's broken rim and looked over. The inner cliffs dropped hundreds of feet (a hundred meters or so) to a circular channel ringing a new mountain rising from the ruins of the old—a huge dome of smoking rock, its summit towering above us.

On the floor of the channel sprawled a field of ice and snow blackened by cinders and split by crevasses that gaped white in the enveloping mists. As we clung to the sharp edge, the dome hurled showers of rock from its steep sides. When large boulders hit the ice below, they left white wounds in the dark surface.

One of Kamchatka's full-time volcanologists is Eugene Vakin. Much of his work has been on Mutnovsky, a complex structure with multiple active craters on a single massif. In March 2000, steam blasts rocked one of the craters while within it a glacier began to collapse. A large section of the glacier vanished, and a green acidic lake, 650 feet (200 meters) in diameter, appeared amid the broken ice. This kind of activity, Vakin told us, indicates that Mutnovsky is heating up and signals the possibility of even bigger eruptions.

We set out just after dawn to follow a turbid river up into that crater. Our path led across slopes of wet, slippery ash, past fumaroles belching steam. Scrambling across the glacier, its surface a mass of dirty ice and cinders, we skirted the lake and climbed to a narrow divide. Standing on ice, we felt the hot breath of fumaroles; around us rose the steep crater walls lined with red and yellow deposits of crystalline sulfur. Slabs of glacier peeled off and crashed into the sour pea green water.