Geology and wine: a review

The geology of wine is important to the wine-maker, but of very little importance to the drinker. However, a geologist with an interest in wine is almost inevitably going to take more than a passing interest in what lies beneath vineyards. This may have resulted in the importance of the geology being over-rated. Many wine writers who are not geologists have dutifully described the geology associated with particular wine regions without actually stating how the geology is important. Jake Hancock was quick to realize that a lot of what is written about geology in wine books is at best misguided and at worst utterly wrong, and set about putting this to rights at every opportunity. Vines derive most of their nourishment from a depth extending down to 0.6 m, but will, most of the time, rely on water from down as far as 2 m for transpiration. Only during periods of drought will they draw significant water from >2 m. Clearly then, in areas where there is a deep cover of drift or a deep soil horizon, geological influence on vines will be minimal. Even where the soil is thin, geology will, in many areas where vines are grown, only control the quality of the grapes indirectly through influence on soil composition, geomorphol-ogy and water retention. These factors will be examined, together with examples of instances where geology does have a direct influence on wine quality.