Geologically, Harbison Estate is related to hillside immediately to the east, spanning to the top of the Vaca Mountains above Oakville. In the book The Winemaker's Dance (University of California Press, 2004), authors Jonathan Swinchatt and David G. Howell theorize on the creation of the Vaca range and attribute it to volcanic activity nearly 150 million years ago. When the peaks became too high and the mountain too heavy, gravity took over and hundreds of feet of iron-rich, red volcanic soil came tumbling down, creating the foundations for what are now a few but critically acclaimed vineyards of legendary Eastern Oakville. Red soils have long been touted as ideal for cultivating Cabernet Sauvignon. Its minerality preserves fruit character and creates wines with great freshness and finely grained tannins. It is with this backbone that the wines of Harbison Estate are created.