The Sonoma Valley AVA centers on the Sonoma Valley (also known as The Valley of the Moon) in the southern portion of the county. The appellation is bordered by two mountain ranges: the Mayacamas Mountains to the east and the Sonoma Mountains to the west. Along with being the area where so much of Sonoma County’s winemaking history took place, the area is known for its unique terroir, with Sonoma Mountain protecting the area from the wet and cool influence of the nearby Pacific Ocean. The Sonoma Mountains to the west help protect the valley from excessive rainfall. The cool air that does affect the region comes northward from the Los Carneros region and southward from the Santa Rosa Plain. Because the valley is cooled from the north and south, it is different from other California north-south-oriented grape growing valleys in the interior. In addition, the daily wind that makes its way into the northern and southern sections of the valley slows ripening, which prolongs hang time and promotes natural balance in the wines. In the appellations of the North Coast, the wind is unique to Sonoma Valley and Carneros. The soils of the Sonoma Valley, like the rest of the county are varied. One finds a wide disparity between valley floor and mountain soils; those found in flatter, valley areas tend to be quite fertile, loamy and have better water-retention while the soils at higher elevations are meager, rocky and well-drained. In general, the structure, rather than the composition of the soil, is the deciding factor where grape plantings are concerned.