Sediment Articles from SEXGRINDER.COM Free Article Directory

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Sediment is any particulate matter that can be transported by fluid flow and which eventually is deposited as a layer of solid particles on the bed or bottom of a body of water or other liquid. Sedimentation is the deposition by settling of a suspended material.

Sediments are also transported by wind (aeolian processes) and glaciers. Desert sand dunes and loess are examples of aeolian transport and deposition. Glacial moraine deposits and till are ice transported sediments. Simple gravitational collapse also creates sediments such as talus and mountainslide deposits as well as karst collapse features. Each sediment type has different settling velocities, depending on size, volume, density, and shape.

Sediment moves in a variety of ways, depending on a balance between the upwards velocity and the settling velocity on the particles in the bed. If the upwards velocity is greater than the settling velocity, sediment will be transported downstream as suspended load. As there will always be a range of different particle sizes in the flow, some will have sufficiently large diameters that they settle on the river or stream bed, but still move downstream. This is known as bed load and the particles are transported via such mechanisms as saltation (jumping up into the flow, being transported a short distance then settling again), rolling and sliding. Saltation marks are often preserved in solid rocks and can be used to estimate the flow rate of the rivers that originally deposited the sediments.

The overall balance between sediment in transport and sediment being deposited on the bed is given by the Exner equation. This equation is important in that changes in flow depth and slope (see depth-slope product) will change the basal shear stress, thus causing local areas of erosion and deposition. More large-scale changes such as dam emplacement and removal and sea-level variation change Base level and cause the river to either pool (and deposit its entire load) or rapidly erode into its underlying substrate.

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