Sediment Transport and Deposition Processes

Transportation

The eroded materials produce waste that can be classified into three types: ions, small particles, and clasts or fragments of different sizes. Depending on their size, detrital or clastic sediments are classified as gravel or ridges, coarse and fine sand, silt, and clay. The sediments are transported to lower areas by conveyor agents. The most important agent is water, followed by wind and glaciers.

In some cases, such as with particles dissolved in water, all transported materials are alike. However, in most cases, the lighter particles reach farther than the heavier ones, which are usually larger. This is known as selective transport, resulting in a selection of materials by size. Transport occurs in three basic ways: in solution, in suspension, and as bedload.

In Solution

This carries water-soluble ions.

In Suspension

This is for very fine solid particles or gels, which float in the water or air. In the case of ice, the fragments may be larger and move up the ice mass, which resists their weight.

As Bedload

Clasts are transported in three ways:

• Saltation: Particles move by jumping on the surface, carried by wind or water.
• Rolling: Particles roll on the surface because the agent cannot lift them.
• Creep: The particles are so heavy that they crawl along the bottom, carried by water, wind, or ice.

Although particle size is a key factor in transportation, current speed is also important. The greater the speed, the farther the *residues* will be transported, and the larger they can be. However, the process is also influenced by other factors, such as the density and shape of the particles. Thus, for particles of equal size, less dense particles will be carried further. Rounded particles will preferably roll, whereas angled particles will jump or crawl.

Sedimentation

Sooner or later, the erosion products cease to be transported and are deposited in *depressed* areas of the Earth's crust, located at variable distances from their origin. Areas where large amounts of sediments accumulate are called sedimentation basins. These are located on continents: plains, lakes, and the lower channels of rivers, streams, and glaciers, but especially in the seas and oceans.