High Valley Vineyard Soil, Terrain & Geology
The Role of Elevation and Soil on High Valley Vineyards & Wine Production
Debris and lava flows from the eruption created the eastern wall of the valley and blocked the natural drainage routes. Round Mountain is now extinct. High Valley is separated from Clear Lake by a ridge created by the same eruption.
The elevation of the AVA ranges between 1,600 and 3,000 feet above sea level. The valley floor is located at about 1,600 to 1,800 feet above sea level which is about 500 to 700 feet higher than Clear Lake. Sauvignon Blanc and Pinot Noir are widely planted in the alluvial soils on the valley floor.
Vineyards are also planted on the ridges that surround the valley at elevations ranging between 2,200 and 2,400 feet. Soils on these ridges are red and volcanic. Cabernet Sauvignon, Syrah, and Zinfandel dominate these hillside areas.
High Valley runs from east to west which is quite unusual for valleys in the Coastal Mountain Range. Most run north to south. The valley is about nine miles long and three miles wide. Schindler Creek is the main watershed and drains to the Clear Lake. But it is not especially effective and the valley floor has a high water table.
After the Round Mountain eruption, water began to pool on the valley floor and most of High Valley became a lake. Schlindler Creek eventually cut its way through the valley walls and drained much of the lake. A large alluvial plain was left behind which is now the valley floor of High Valley. Tule Lake is a remnant of the much larger body of water which once existed on the valley floor.
This pooling of water has had a major impact on High Valley’s topography and soil. A large amount of sediment and alluvium was deposited on the valley floor and surrounding canyons. The constant percolation of water through the ground has made soil aerated and well drained. Natural springs are common and growers are able to easily tap this water for irrigation.
Soil on the valley floor is made of clay, sand, and loam. This soil type is known as Wolfcreek Loam. It does not drain as well as hillside soils but is still sufficiently porous for growing certain varietals.
The Franciscan Complex makes up much of the parent material for the soil in southwestern parts of High Valley. The Franciscan Complex can be found throughout California and dates to the Jurassic Period. It is made mainly of weathered sandstone and shale.
Basalt is very common in eastern parts of the valley. The eruption of the Round Mountain Volcano mainly affected the soil in the eastern part of High Valley. A layer of volcanic cinders and pumice sits over the top of basalt in the eastern part of the AVA.
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