On the slopes of Japan's Mount Aso – clouds of steam and smoke billowing, smell of sulfur, cold wind blasting grit, stinging, ears burning, a boulder drew me in, its presence marked place. The image stayed with me hours later as the heat of a bath, outdoors, seeped bone-deep in the chill air of October; the smell of sulfur linked volcano and hot spring, violence and repose.

How to account for the rock's rounded shape and reddish color, its fine-grained, porous texture, so different from the rocks of the surrounding peaks, dark and jagged?

Months later, this rock led me to learn more. Its form, color, and position hold a memory of water, red-hot rock, fountains of fire. It is a big cinder, a "bomb" blown out of the earth when magma met water where tectonic plates collide, beneath Japan, along the Ring of Fire, birthplace of land, sea, and air.