The Lay of the Land
The Lay of the Land
Every farmer knows that certain crops do better in particular fields, and every gardener knows that some plants grow better in certain spots in the garden. Grapevines are no different. The idea forms the basis of the concept of terroir, and in this and the following two chapters we will meet a number of factors, besides the minerals and rocks we have been talking about, that contribute to it. First, we consider the shape of the land surface. The weathering of rocks produces loose debris–sediment–which sooner or later will move, and this gives rise to erosion. The two processes usually work hand in hand though, strictly speaking, weathering happens in place, whereas erosion results from movement of the debris. We will look more closely at weathering in the next chapter, in the context of generating soil. Here we are concerned with erosion. It may involve sand particles being hurled at outcrops by high winds, or rivers loaded with particles grinding at the land to form a river channel. In some places, rock-charged ice may be gnawing away at the bedrock. Ultimately, the shape of the land surface is the result of how such processes interact with the solid bedrock. In other words, the interplay between erosion and bedrock determines the physical lay of vineyards. Plateaus are level upland areas. They can be formed in any kind of material: it’s the flat, table-like form that defines them. For instance, a vast area of the Deccan Plateau of central India, focus of a burgeoning wine industry, is made up of horizontal flows of basalt lava. The Colorado Plateau in the United States is formed largely of horizontal sedimentary strata. It has been deeply incised by rivers, in places leaving isolated blocks such as mesas and buttes (Figure 8.1; see Plate 18). Mesas have a larger summit area than buttes, compared to their heights. These bodies of rock have not been individually uplifted, as is sometimes claimed. They are remnant blocks, erosion having taken away the strata that were once around them.
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