The valley's wines vary, region by region. Learn the flavor profiles to guide your choice.All that Napa Valley is — its glitz and glamour, come-hither grip on wine country trippers, its stratospheric prices — it owes to its dirt. Vineyard farmers have identified more than 30 soil types in Napa Valley, from well-drained gravelly loams to moisture-retaining silty clays, born of volcanoes, maritime wash and alluvial drainage many millions of years ago. The depth and kind of soil, its water-holding capacity and its chemistry all affect those laurelled Napa Valley vines that grow on and in it.