Different sediment types have different densities depending on their previous geological history, the chemical properties, the organic content and several other factors.
If the area of interest is large it may be necessary to obtain knowledge of sediment in different locations within the area in order to generate a representative density map of the area for each layer. This can be done from either measurements or through researching the geological history of the area. In the vertical the density varies with the degree of compression and with the type of mud. Different geological periods have left soils with different densities. For instance areas that have been covered by glaciers can have very hard layers, and areas that has been sedimentation areas for a long time can be covered by relatively loose mud. Therefore it is necessary to assess the density and the strength at different depths of the seabed in order to determine the vertical resolution of the bed and the bed densities for each layer.
The bed density is defined as dry density as follows:
(5.1)
