You really cannot decribe a vineyard without commenting on the soils where the grapes grow. The Speedy Creekvineyard site is about 10 miles south of Mount Saint Helena. This peak in the Mayacmas Mountains flanks Napa, Sonoma, and Lake counties of California. Composed of uplifted 2.4-million-year-old volcanic rocks from the Clear Lake Volcanic Field, it is one of the few mountains in the San Francisco Bay Area to receive any snowfall during the winter.

The Clear Lake Volcanic Field is located besides Clear Lake in California's northern Coast Ranges. The site of late-Pliocene to early Holocene activity, the volcanic field consists of lava domes, cinder cones, and maars with eruptive products varying from basalt to rhyolite The field's magma chamber also powers a geothermal field called The Geysers, which hosts the largest complex of geothermal power plants in the world. These can generate approximately 2000 megawatts, enough to power two cities the size of San Francisco.

Soils at the vineyard site are predominately derived from rhyolite which is commonly referred to volcanic ash or tuffa. With the right combination of tractor work and lime addition, the light wight rock can be brokedown to yield a sandy-loam type soil. Lime additions are needed to raise the soil pH to fertile levels, and the soils have a low water holding capacity. Soil depth may vary based on historic landslides events and previous geological activity which defined much of the surrounding landscape in Knights, Franz, and Napa Valleys.

This hillside site contains very little flat ground and that creates a farming challenge. Some vineyard blocks are located on hillsides with up to 25% slopes. Driving a tractor presents a challenge, and you don't need to hit the stairmaster after walking through the vineyard all day. The characteristics associated with of the vineyard soil and hillside location produce a terroir unique to Knight Valley and Speedy Creek.