Flachlage

Flachlage is a geological term used primarily in German-speaking contexts to describe bedding planes or stratified rock units that lie nearly horizontal. The word translates as "flat position" and denotes a bedding attitude with only a small inclination from the horizontal. Flachlage contrasts with steeper dips typical of folded or faulted zones.

Formation and occurrence: Flat-lying strata form where sediments are deposited in relatively quiet environments such as lakes, shallow seas, or broad floodplains, allowing horizontal layering to remain after lithification. They can also persist when tectonic tilting after deposition is minor or has been subsequently reset by tectonic relaxation.

Measurement and classification: In the field, bedding orientation is described by strike and dip. A flachlage implies a small dip angle, with beds approaching horizontal. The exact threshold varies by author and region, but the concept centers on near-horizontal orientation rather than a precise degree cut-off.

Implications: Flachlage affects hydrogeology, foundation design, and mining or quarry planning, because horizontal layers influence groundwater flow, rock strength, and the pattern of excavation difficulties.

Terminology: In English-language literature the same idea is described as flat-lying or horizontally bedded strata. Flachlage remains common in German geology to emphasize the horizontal orientation of beds within a formation or region.