Topography and Geology 'White Bluffs AVA is located on a broad elevated
plateau that rises, on average, above the surrounding landscape. The Ringold and Koontz
Coulees divide the plateau into two distinct areas capped by flat regions with relatively even surfaces and south-facing slope aspects. Elevations within the area range from in the coulees to approximately in the northeastern section of the AVA. The majority of the AVA has elevations between . By contrast, the regions surrounding the AVA are on the
Columbia Valley floor and lower elevations. According to the petition, the relatively flat terrain of the AVA provides gently sloping vineyard sites. Southern aspects allow vines to absorb more
solar energy per unit area than regions without a southern aspect. Greater solar energy absorption promotes an earlier onset of
bud break,
flowering,
veraison, and
harvest. The petition also states that vineyards planted on the plateau have a longer growing season than vineyards on the valley floor, where cold air pools and increases the risk of frost.
Soil Beneath White Bluffs AVA is a thick layer of
sedimentary rocks called the Ringold Formation, which was formed in lakes and rivers between 8.5 and 3.4 million years ago. The Ringold Formation overlies the Columbia River
basalt bedrock. The upper part of the Ringold Formation contains an erosion-resistant layer commonly referred to as
caliche. This layer reaches depths of at least and limits root penetration and the water-holding capabilities of the soil. As a result, areas with thick layers of caliche must undergo ripping with bulldozers to break up the caliche before planting vineyards. By contrast, the Ringold Formation and the caliche layer are much thinner or entirely absent in the regions surrounding White Bluffs AVA, allowing roots to come into contact with the basalt bedrock and a variety of minerals including
olivine and
plagioclase feldspar. The soils of the AVA derive from wind-deposited
silt and
fine sand overlying sediment deposited by
ice-age floods. Most of the flood sediment is a mixture of silt and sand that settled out of suspension in
glacial Lake Lewis. The thickness of the flood
sediment gradually increases with decreasing elevation since there were multiple
ice-age floods of varying intensity, and the lower elevations were flooded more frequently. As a result, the soil depths on the plateau that comprises the AVA are likely to be thinner than those of the surrounding valley floor. The thinness of the soils in White Bluffs AVA allows roots to reach the clay-rich Ringold Formation. High clay content allows the soils to release water more slowly than sandier soils, putting less stress on grapevines during dry conditions.
Climate The petition states that White Bluffs AVA has a longer growing season than the surrounding regions. According to the petition, the longer growing season means that the AVA is less prone to spring frosts that can damage the vines after bud break and are also less likely to experience fall frosts that halt the ripening process and delay harvest. The growing season within the AVA averages 237.5 days, while the region to the north averages 200 days. The region to the east averages 169 days, and the region to the south averages 191 days. Climate data was unavailable for the area west of the appellation. ==Industry==