The other day I visited Valle Grande, part of the Valles Caldera volcanic region in New Mexico. I have a personal association with the place: my grandfather, the geologist Clarence Samuel Ross, spent many years analyzing the caldera, and asked that his ashes be scattered here. Craig Martin's history of Valle Grande, which I picked up at the Valles Caldera National Preserve gift shop, reports that my grandfather first explored the area in the 1920s, on horseback, and "was the first to recognize the connection between large-volume ash flows and the formation of calderas." He also made a pioneering analysis of trinitite, the mineral formed in the first atomic blast at White Sands. I have only faint memories of him — he died in 1975, at the age of ninety-four — but I was happy to learn from my father that Willa Cather's Death Comes for the Archbishop was one of his favorite books; it is also one of mine.