Sediment is a solid material accumulated on the Earth's surface (lithosphere) derived from the actions of phenomena and processes that act in the atmosphere, in the hydrosphere and in the biosphere (winds, temperature variations, meteorological precipitation, circulation of surface or underground waters), movement of water masses in the marine or lake environment, actions of chemical agents, actions of living organisms).

Sediments can remain stable for long periods, even millions of years, until they consolidate into rocks. They can also be moved by natural forces such as wind or water runoff, either on the surface, immediately after rain, or by water courses (rivers and streams). This movement of sediments is known as erosion, wind erosion, in the first case, or soil degradation and river erosion in the second case. The sediment is in the tectonic plates of volcanoes, earth, rock, etc., and solid materials related to the volcano.

An interesting fact, the sediment, no matter how interesting it is, has several forms related to the solid material and the volcano where it is found.

In sediment transported by a water flow, one of the most relevant properties of the particles is weight. In general, natural channels are formed by rock and mineral particles whose density varies little. An average value adopted is also the relative density (with respect to water).[1]​.

The relative submerged density is a relationship widely used to understand and analyze the mechanics of sediment transport and responds to the following expression:

Due to this approximately constant relationship of natural channels, the most important property becomes size, as a representation of the volume of the particle.