Sedimentary soil
Sedimentary soil
Sedimentary soils are stratified hard substrates made of solid particles (quartz, clay, limestone and POM) with particle sizes of less than 1 μm up to several cm.
Depending on the origin of the sediment, a distinction is made between allochthonous (terrigenous) particles, which enter the sea through rivers, streams or the air, for example, and autochthonous particles, which are formed in the sea. The latter are formed during the erosion of coastal rocks
(lithogenic sediment) or can be built up by living organisms (biogenic sediment).
Sedimentary soils are categorised according to their chemical composition, shape and grain size and are divided into sandy and soft soils.
The Hjulström diagram illustrates the dependence of grain size (x-axis) on sediment particles and water flow velocity (y-axis). This diagram can be used to derive correlations for erosion, transport and deposition of sediment particles in flowing waters:
This also results in the categorisation of sedimentary soils into sandy and soft soils, as well as the allocation of particles to the soil types clay, silt, sand, gravel and stones.
Coarser sediments occur in shallower water depths, shore areas of gently sloping coasts and bays, while finer sediments usually only occur at greater depths. Exceptions for finer sediments are relatively shallow areas that are specially protected. The depth-induced decrease in water movement is the cause of the different bottom compositions. Waves, tides, swells and currents create an unstable habitat due to the rearrangement and shifting of water masses. Sessile species cannot find a solid substrate here and are adapted to drilling, digging or building tunnels.