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    Volcanic soils

    Basalt, ash and lapilli: light, porous soils born of eruptions.

    Volcanic soils in the atlas

    1. Atlas regionNapa Valley
    2. Atlas regionTokaj

    Atlas regions where this rock appears in the text or the soil profile.

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    What it is

    Basalt is the most common volcanic rock: generally fine-grained, dark and heavy, formed when erupted lava cools. Tuff is rock formed from consolidated volcanic ash.1

    volcanic rock
    gravel
    clay

    Schematic: how fast water drains through the rock. A qualitative comparison based on the sources on this page.

    For the vine

    In the Canary Islands, basalts, trachytes and phonolites give light, porous soils that drain well, prevent waterlogging and encourage deep roots.2 In Oregon's Willamette Valley, volcanic soils carry kaolinite clays, while soils on marine sediments carry smectite clays.3

    In Napa Valley volcanic and marine soils sit side by side.4

    Regions

    Sources

    1. USGS Bulletin 1309, The Geologic Story of Isle Royale National Park — Glossary. U.S. Geological Survey (mirrored on npshistory.com). level 4 · checked 2026-10-13
    2. Wines of Fire and Earth: Exploring the Volcanic Terroirs of the Canary Islands – a Case Study (Kreidlmayer, Ecocycles 11(3):38-59). Ecocycles, 2026. level 3 · checked 2026-10-13
    3. The Terroir of Pinot Noir Wine in the Willamette Valley, Oregon (Barnard & Burns, Portland State University; IVES Terroir congress proceedings). IVES Open Science, 2016. level 3 · checked 2026-10-13
    4. Soils and geology. Napa Valley Vintners. level 4 · checked 2026-10-13
    5. On rocky ground: The science of soil and wine taste (Prof. Alex Maltman). Decanter, 2018. level 4 · checked 2026-10-13