Geography, Geology and Terroir
The geography of the wine growing area in Alsace is determined by two main factors, the Vosges mountains in the west and the Rhine river in the east. The vineyards are concentrated in a narrow strip, running in a roughly north-south direction, on the lower eastern slopes of the Vosges, at altitudes of 175–420 m. Those altitudes provide a good balance between temperature, drainage and sun exposure under Alsace's growing conditions. Because of predominantly westerly winds, the Vosges mountains tend to shelter Alsace from rain and maritime influence, and the region is therefore rather dry and sunny. Rainfall in Colmar is 500 mm, but can vary greatly between sites. While the slope down the Vosges is generally east-facing, many of the best sites are south-west to south-east facing, and benefit from extra sun exposure.
Alsace's geology is quite varied, with many different kinds of soils represented in the vineyards. Alsace’s soils are a result of its location at a geological fault. Alsace as a whole is located on the western part of the Rhine Graben, which is the result of two systems of parallel faults, with a dropped down block between the Vosges and the Black Forest.
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