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Napa Valley · Section through Calistoga and Howell Mountain

Calistoga to Howell Mountain: ash, gravel and lava

Across the top of the valley at Calistoga, over the river gravels, up the Crystal Springs slopes and onto the volcanic plateau of Howell Mountain. Tap a layer to read it.

Swipe the plate sideways to see the whole section.

Schematic. The line runs west to east at about 38.57° N, from the Diamond Mountain side to the east edge of the Howell Mountain plateau. Calistoga, Crystal Springs and Lotus lie 1–2.5 km off the line and are drawn where they project. All the bedrock here belongs to the Sonoma Volcanics; the order of tuff and lava beds changes from place to place and is drawn as a simple stack. The Howell Mountain floor is the 1,400 ft contour. Check against the USGS Napa map (Graymer and others, 2007). Heights from AWS terrain data. Blueline and Cloudy’s, in Dutch Henry Canyon, and the St. Helena vineyards lie 1–8 km south of the line and are shown dashed where they project; Cloudy’s and Barbour are placed approximately.

Key to the ground

5 layers, youngest at the top

    Single vineyards we pour from. Tap one on the plate.

    Why the floor and the mountain differ

    1. Calistoga’s floor heats hard by day, then cool air arrives at night through the Chalk Hill gap: a wide swing.
    2. Howell Mountain sits above the fog; days are cooler and nights milder, so the swing is narrow.
    3. Floor gravels drain fast but are deep; mountain soils are thin over broken lava and tuff.
    4. Crystal Springs’ west-facing slopes catch the afternoon sun and sit above the frost that pools below.

    Did you knowHowell Mountain was Napa’s first sub-appellation, approved in 1983. Its lower edge is the 1,400 ft contour, said to be roughly where the summer fog tops out.

    In the book

    Pas Mal wines on this ground

    Calistoga

    Crystal Springs and St. Helena

    Howell Mountain

    Sources: USGS Scientific Investigations Map 2918, geologic map of the Napa 1:100,000 area (Graymer and others, 2007); TTB final rule, Crystal Springs of Napa Valley AVA (2024); Howell Mountain Vintners and Growers, facts and FAQs; Napa Valley Vintners, Calistoga AVA; Hourglass and DANA Estates vineyard notes; Bacio Divino, Cloudy’s technical sheet (2009); Wine With Seth and Napa Wine Project, Hourglass notes; AWS Terrain Tiles.