the foothill regions where the AVA is located and the lava flows created ‘basal lava fingers’ which can be seen amongst marine soils in the McMinnville AVA vineyards. The soils are primarily uplifted marine sedimentary loams and silts, with alluvial overlays. Beneath is a base of the uplifting basalt. Clay and silt loams average 20-40 inches in depth before reaching harder rock and compressed sediments, shot with basalt pebbles and stone. The uniqueness of the soils for winegrowing is in the 20 to 40 inch depth.
Climatically, this AVA is again in a class of its own. These primarily east and south facing slopes facing sit in a protected weather shadow of the Coast-range Mountains. Rainfall is lower (33 inches annually) than sites only 12 to 20 miles to the east. The foothills also provide protection from chilling winds in the unstable air conditions of the spring and fall. Winegrowers also have the option of placing vineyards on more southerly facing sites to take advantage of the drying winds from the Van Duzer corridor, which helps control mold and mildew on the grapes during Oregon’s humid summer days.Of greatest note are the flavor qualities of the Pinot noirs from these soils, which are highly pigmented with a strong backbone of tannins and acidity and a massive palate of black fruit, spice, and earthy flavors. White wines from the Pinot family and other Northern European Cultivars, including Pinot Gris, Pinot Blanc and Riesling, have similar personalities, and are noted for their brightness, texture, and fruit forward profiles. There are currently over 600 acres of wine grapes planted within the AVA. Seven wineries currently produce wine within the AVA and over twenty other wineries make wine from fruit sources from the region.
The Willamette Valley And McMinnville AVA
The Willamette Valley is the most populated region in the state of Oregon. Located in the state's northwest, the region is surrounded by tall mountain ranges to the east, west and south. The valley's floor is broad, flat and fertile because of Ice Age conditions. Located centrally inside the large alluvial-deposited soils of the Willamette River drainage basin, the valley spreads far from the river banks to both the east and west barrier ranges as the river proceeds northward from its emergence from the Calapooya Mountains near Eugene to the confluence of the Willamette with the Columbia River at Portland. The valley's waterways and tributary streams and valleys were of great importance for water transport in the development of the Oregon Territory.
Much of the Willamette’s fertility is derived from a series of massive ice age floods that came from Glacial Lake Missoula in Montana and scoured across Eastern Washington, sweeping its topsoil down the Columbia River Gorge. When floodwaters met log-and-ice jams at Kalama in southwest Washington, the water caused a backup that filled the entire Willamette Valley to a depth of 300 to 400 feet (91 to 120 m) above current sea level. Some geologists suggest that the Willamette Valley flooded in this manner multiple times during the last ice age.
The agricultural richness of the valley is in part a result of the Missoula Floods, which inundated the valley approximately forty times between 15,000 and 13,000 years ago at the end of the last ice age. The floods were caused by the periodic rupturing of the ice dam of Glacial Lake Missoula, the waters of which swept down the Columbia River and flooded the Willamette Valley as far south as Eugene. The floodwaters carried rich volcanic and glacial soil from Eastern Washington, which was deposited across the valley floor when the waters subsided. The soil in the Willamette Valley is about 0.5 miles (1 km) deep in some areas.
Characterized by cool, wet winters and warm, dry summers, the Willamette Valley's climate is relatively mild throughout the year. It has been described as Mediterranean, though somewhat cooler and wetter. Most valley precipitation arrives as rain, about half of which falls between December and February. Growing seasons are long, averaging 150 to 180 days per year in the lowlands to about 110 to 130 days at elevations above 800 feet. Precipitation varies considerably from place to place within the valley. Average annual totals range from less than 40 inches at low elevations to more than 80 inches in the foothills of the Cascade and Coast ranges.
McMinnville is the county seat and largest city of Yamhill County. According to Oregon Geographic Names, it was named by its founder, William T. Newby (1820–1884), an early immigrant on the Oregon Trail, for his hometown of McMinnville, Tennessee. McMinnville is located at the confluence of the North and South Forks of the Yamhill River in the Willamette Valley. Since the 1990s, the majority of the vineyards of the Willamette Valley American Viticultural Area (AVA) are in the area surrounding McMinnville, thus giving this city a claim to the title of the capital of Oregon's wine industry. In January 2005, a McMinnville AVA was established. The AVA includes 14 wineries, the first of which was Yamhill Valley Vineyards, and 523 acres (2.12 km2) within the Willamette Valley AVA.
The McMinnville AVA lies due west of the town of McMinnville in the Coast Range Foothills of Yamhill County. This AVA is the most westerly of all Oregon AVAs and is geologically and climatically very different from any other in the Willamette Valley. Geologically, the soils in the McMinnville AVA are the oldest and most complex of any Oregon AVA, with a combination of marine sedimentary soils and basalt. The soils were created during the Eocene period 38-55 million years ago and were the result of a combination of Cascade Mountain lava flows and tectonic plate movements that created the Coast Range Mountains. The plate movement exposed ancient and weathered soils in