North & Baltic Sea Geology
Understanding of the geologic conditions in the shallow subsurface are key for the planning, design and layout of windmill foundations. Costs are affected by the properties of the subsoil as much as by the uncertainty. Accordingly, methods are required to constrain the properties and measure parameters which can be related e.g. to the shear strength.
The classical approach is based on coring or probing at designeted wind mill locations, For this, platform for drilling or cone penetrations tests or a combination of both are required. However, in the course of wind farm planning, the layout of wind mill positions may change, and accordingly, also subsurface imaging data from (multichannel) seismic surveys became more and more importat to allow extrapolation of point information along a seismic line.
Scientifically speaking the geology associated with German waters is very complex, since very different processes and boundary conditions have to be considered. On the one hand, bedrock geology varies from Pleistocene age in the West to Cambrian and Precambrian ages to the East. And their properties vary accordingly, which has relevance for the choice and layout of wind mill foundations. In the North Sea Basin, salt movement continues into recent time, and tectonic activity affects the soil ages and properties.
A major impact on the shallow subsurface was originating from glacial activities, like subglacial erosion, basal erosion, glaciotectonicsm, deglaciation and associated deposition or moraines and glaciofluvial materials. Concurrently with climatic cycles, also sea level changes played a role and cause a transition from a terrestrial to a marine or estuarine setting during deglaciation in the North Sea, while in the Baltic Sea the isostatic rebound led to intemittent connection to the salty ocean, causing switches betwen freshwater and brackish condition with significant hydrological and geochemical gradients developing within the Baltic Sea.