Sediment

Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice or by the force of gravity acting on the particles. For example, sand and silt can be carried in suspension in river water and on reaching the sea bed deposited by sedimentation. If buried, they may eventually become sandstone and siltstone through lithification.

Types of Sediment

Sediments are most often classified by particle size, but can also be classified by the processes that cause the sedimentation and by the types of material in the sediment. The types of sediment include:

• Terrigenous Sediment: This type of sediment is sourced from the land and transported by water to the place of deposition. It is the most common type of sediment, and includes boulders, pebbles, gravel, sand, silt, and clay.

• Biogenous Sediment: This type of sediment is made up of the skeletal remains of plants and animals. Most common are the microscopic, calcium carbonate shells of diatoms and foraminifera.

• Hydrogenous Sediment: This type of sediment is precipitated directly from water. It includes manganese nodules, calcium carbonates, metal sulfides, and evaporites.

• Cosmogenous Sediment: This type of sediment is derived from outer space. It includes micrometeorites and cosmic dust.

Sediment Transport and Deposition

Sediment transport and deposition are key aspects of sedimentology. They are governed by several factors, including the size and density of the particles, the velocity and direction of the transporting medium, and the characteristics of the depositional site.

Sedimentation in Human History

Sedimentation has played a significant role in human history, as it has influenced the distribution of soil fertility, the flow of rivers, the siting of cities, and the form of human habitation.

See Also

• Erosion
• Weathering
• Sedimentary rock
• Sedimentology
• Soil erosion

References

Sediment Resources
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