![Sediment plume at sea](https://upload.wikimedia.org/wikipedia/commons/6/63/Sediment_plume_at_sea.jpg)
Sediment is a naturally occurring material that is broken down by processes of
weathering
Weathering is the deterioration of rocks, soils and minerals as well as wood and artificial materials through contact with water, atmospheric gases, and biological organisms. Weathering occurs ''in situ'' (on site, with little or no movement) ...
and
erosion
Erosion is the action of surface processes (such as water flow or wind) that removes soil, rock, or dissolved material from one location on the Earth's crust, and then transports it to another location where it is deposited. Erosion is dis ...
, and is subsequently
transported
''Transported'' is an Australian convict melodrama film directed by W. J. Lincoln. It is considered a lost film.
Plot
In England, Jessie Grey is about to marry Leonard Lincoln but the evil Harold Hawk tries to force her to marry him and she w ...
by the action of wind, water, or ice or by the force of
gravity
In physics, gravity () is a fundamental interaction which causes mutual attraction between all things with mass or energy. Gravity is, by far, the weakest of the four fundamental interactions, approximately 1038 times weaker than the stro ...
acting on the particles. For example,
sand
Sand is a granular material composed of finely divided mineral particles. Sand has various compositions but is defined by its grain size. Sand grains are smaller than gravel and coarser than silt. Sand can also refer to a textural class o ...
and
silt
Silt is granular material of a size between sand and clay and composed mostly of broken grains of quartz. Silt may occur as a soil (often mixed with sand or clay) or as sediment mixed in suspension with water. Silt usually has a floury feel ...
can be carried in
suspension
Suspension or suspended may refer to:
Science and engineering
* Suspension (topology), in mathematics
* Suspension (dynamical systems), in mathematics
* Suspension of a ring, in mathematics
* Suspension (chemistry), small solid particles suspende ...
in river water and on reaching the sea bed deposited by
sedimentation
Sedimentation is the deposition of sediments. It takes place when particles in suspension settle out of the fluid in which they are entrained and come to rest against a barrier. This is due to their motion through the fluid in response to the ...
; if buried, they may eventually become
sandstone
Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks.
Most sandstone is composed of quartz or feldspar (both silicates ...
and
siltstone (
sedimentary rock
Sedimentary rocks are types of rock that are formed by the accumulation or deposition of mineral or organic particles at Earth's surface, followed by cementation. Sedimentation is the collective name for processes that cause these particles ...
s) through
lithification
Lithification (from the Ancient Greek word ''lithos'' meaning 'rock' and the Latin-derived suffix ''-ific'') is the process in which sediments compact under pressure, expel connate fluids, and gradually become solid rock. Essentially, lithificatio ...
.
Sediments are most often transported by water (
fluvial processes
In geography and geology, fluvial processes are associated with rivers and streams and the deposits and landforms created by them. When the stream or rivers are associated with glaciers, ice sheets, or ice caps, the term glaciofluvial or fluvio ...
), but also wind (
aeolian processes
Aeolian processes, also spelled eolian, pertain to wind activity in the study of geology and weather and specifically to the wind's ability to shape the surface of the Earth (or other planets). Winds may erode, transport, and deposit mate ...
) and
glacier
A glacier (; ) is a persistent body of dense ice that is constantly moving under its own weight. A glacier forms where the accumulation of snow exceeds its ablation over many years, often centuries. It acquires distinguishing features, such as ...
s. Beach sands and
river channel deposits are examples of fluvial transport and
deposition, though sediment also often settles out of slow-moving or standing water in lakes and oceans. Desert sand dunes and
loess are examples of aeolian transport and deposition.
Glacial
A glacial period (alternatively glacial or glaciation) is an interval of time (thousands of years) within an ice age that is marked by colder temperatures and glacier advances. Interglacials, on the other hand, are periods of warmer climate betwe ...
moraine deposits and
till
image:Geschiebemergel.JPG, Closeup of glacial till. Note that the larger grains (pebbles and gravel) in the till are completely surrounded by the matrix of finer material (silt and sand), and this characteristic, known as ''matrix support'', is d ...
are ice-transported sediments.
Classification
![Sediment off the Yucatan Peninsula](https://upload.wikimedia.org/wikipedia/commons/0/01/Sediment_off_the_Yucatan_Peninsula.jpg)
Sediment can be classified based on its
grain size, grain shape, and composition.
Grain size
Sediment size is measured on a log base 2 scale, called the "Phi" scale, which classifies particles by size from "colloid" to "boulder".
Shape
![Rounding & sphericity EN](https://upload.wikimedia.org/wikipedia/commons/c/c1/Rounding_%26_sphericity_EN.svg)
The shape of particles can be defined in terms of three parameters. The ''form'' is the overall shape of the particle, with common descriptions being spherical, platy, or rodlike. The ''roundness'' is a measure of how sharp grain corners are. This varies from well-rounded grains with smooth corners and edges to poorly rounded grains with sharp corners and edges. Finally, ''surface texture'' describes small-scale features such as scratches, pits, or ridges on the surface of the grain.
Form
Form (also called ''sphericity'') is determined by measuring the size of the particle on its major axes.
William C. Krumbein
William Christian Krumbein (January 28, 1902 – August 18, 1979) was a notable geologist, after whom the Krumbein Medal of the International Association for Mathematical Geology (IAMG) was named. This medal was established at the 25th Internati ...
proposed formulas for converting these numbers to a single measure of form, such as
: