Geology and wine 3: Terroirs of the Walla Walla Valley appellation, southeastern Washington State, USA

Terroir of the Walla Walla Valley appellation of Washington St are is influ enced by 1) the rain shadow effect and volcanic tephra of the Cascade Mount ain Range, 2) soils derived from Quaternary glacial sediments and wind-blow n loess overlying Miocene basalt, and 3) a warm, dry climate with abundant sunshine and cool nights due to high latitude (45-48 degreesN) and elevatio n. Wine flavours of Walla Walla Valley varierals (including Caberner Sauvig non, Chardonnay, Merlot, and Syrah) appear to be influenced by low humidity , long growing season (1500-1800 degreesC degree days), soil type and drain age, drip irrigation, pruning to restrict vine vigour, trellising methods, and overall topographic climatic setting of the vineyards. Microclimates wi thin the Walla Walla Valley appellation, combined with variations in soil a nd bedrock stratigraphy, yield a range of wine styles as great as many larg er regions and some countries.