Dixon breathes rapidly and as deeply as he can in the cold, oxygen-depleted air. Lithe and 47 years old, he has just climbed 1,000 feet up a dull charcoal-gray slope. Virtually nothing is alive here except Dixon and his group. They are nearly three miles above sea level. The temperature is close to freezing.
Smoke billows from above.
Newly minted rocks litter the mountain. The surface is covered by a blanket of volcanic ash. Walking through this blanket, especially in low oxygen conditions, is like slogging through a desert. They must rest often, and the view is magnificent and terrifying. Nearly everything worth seeing is far below, Mexico City browned by smog, and villages and forests, and ancient mud flows propelled by this volcano.