Old Faithful Geyser and the Geothermal Valley

The geyser erupting a few hundred yards from this road is not a tourist gimmick built on top of a municipal water pipe. It is one of only three so-called faithful geysers in the world, meaning it erupts on a regular interval rather than randomly. The interval here is roughly thirty to forty minutes, driven by a geothermal system that runs deep under the Mayacamas Mountains and expresses itself across the Calistoga area in hot springs, mud pools, and this column of two hundred degree water shooting forty or fifty feet into the air.

The geology that produces the geyser is the same geology that makes this end of Napa Valley distinct from every other wine region in California. The volcanic activity that built the Mayacamas range also created a valley floor with unusual thermal properties, warming the soil faster in spring and retaining heat into the fall harvest season. Winemakers prize this microclimate for the effect it has on grape development, particularly for cabernet sauvignon, which needs a long, warm growing season to develop complex flavors without losing acidity.

This is also the geology that is becoming a complicating factor. A warming climate, combined with a valley that was already warmer than adjacent growing regions, is beginning to push the upper end of Napa Valley into temperature ranges that stress grapevines in summer. The same volcanic heat that made Calistoga a resort destination in Sam Brannan's era and a wine-growing paradise in the twentieth century is becoming, in the twenty-first, an amplifier of an already accelerating problem.

The Wappo people who lived in this valley for thousands of years before the Spanish arrived used the hot springs here. Their specific relationship to the geothermal landscape is a gap in the available documentary record that the research for this track acknowledges without filling.