"All grapes have an affection for gravel, slate or stony soils as all the preferred acres are so infertile and stony that a corn farmer would not even take them as a gift," notes Jeff Cox in his book From Vine to Wine - A complete Guide to Growing Grapes where he discusses the latitudes and altitudes for growing grapes.
Is one plot of land so much different from another? The French word Terroir has no direct translation in English, but is defined as the complete natural environment, including factors such as the soil, topography and climate.
A geology survey of topography shows all contours and elevation chagnes which comprise the second factor of Terroir.
I'm busy working on my blog posts. Watch this space!