Cobbles on a beach

River Rhône flowing into Lake Geneva

Sediment billowing out from Italy's shore into the Adriatic

Sediment, a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of fluids such as wind, water, or ice, and/or by the force of gravity acting on the particle itself.

Sediments are most often transported by water (fluvial processes), wind (aeolian processes) and glaciers. 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 ocean dunes and loess are examples of aeolian transport and deposition. Glacial moraine deposits and till are ice-transported sediments.

Classification[link]

Sediment can be classified based on its grain size and/or its composition.

Grain size[link]

Sediment in the Gulf of Mexico

Sediment off the Yucatán Peninsula

Sediment size is measured on a log base 2 scale, called the "Phi" scale, which classifies particles by size from "colloid" to "boulder".

Composition[link]

Composition of sediment can be measured in terms of:

• parent rock lithology
• mineral composition
• chemical make-up.

This leads to an ambiguity in which clay can be used as both a size-range and a composition (see clay minerals).

Sediment transport[link]

Sediment builds up on human-made breakwaters because they reduce the speed of water flow, so the stream cannot carry as much sediment load.

Glacial transport of boulders. These boulders will be deposited as the glacier retreats.

Sediment is transported based on the strength of the flow that carries it and its own size, volume, density, and shape. Stronger flows will increase the lift and drag on the particle, causing it to rise, while larger or denser particles will be more likely to fall through the flow.

Fluvial processes: rivers, streams, and overland flow[link]

Particle motion[link]

Rivers and streams carry sediment in their flows. This sediment can be in a variety of locations within the flow, depending on the balance between the upwards velocity on the particle (drag and lift forces), and the settling velocity of the particle. These relationships are given in the following table for the Rouse number, which is a ratio of sediment fall velocity to upwards velocity.

Failed to parse (Missing texvc executable; please see math/README to configure.): \textbf{Rouse}=\frac{\text{Settling velocity}}{\text{Upwards velocity from lift and drag}}=\frac{w_s}{\kappa u_*}

where

• Failed to parse (Missing texvc executable; please see math/README to configure.): w_s

is the fall velocity

• Failed to parse (Missing texvc executable; please see math/README to configure.): \kappa

is the von Kármán constant

• Failed to parse (Missing texvc executable; please see math/README to configure.): u_*

is the shear velocity

If the upwards velocity approximately equal to the settling velocity, sediment will be transported downstream entirely as suspended load. If the upwards velocity is much less than the settling velocity, but still high enough for the sediment to move (see Initiation of motion), it will move along the bed as bed load by rolling, sliding, and saltating (jumping up into the flow, being transported a short distance then settling again). If the upwards velocity is higher than the settling velocity, the sediment will be transported high in the flow as wash load.

As there are generally a range of different particle sizes in the flow, it is common for material of different sizes to move through all areas of the flow for given stream conditions.

Fluvial bedforms[link]

Modern asymmetric ripples developed in sand on the floor of the Hunter River, New South Wales, Australia. Flow direction is from right to left.

Sinuous-crested dunes exposed at low tide in the Cornwallis River near Wolfville, Nova Scotia

Ancient channel deposit in the Stellarton Formation (Pennsylvanian), Coalburn Pit, near Thorburn, Nova Scotia.

Sediment motion can create self-organized structures such as ripples, dunes, antidunes on the river or stream bed. These bedforms are often preserved in sedimentary rocks and can be used to estimate the direction and magnitude of the flow that deposited the sediment.

Surface runoff[link]

Overland flow can erode soil particles and transport them downslope. The erosion associated with overland flow may occur through different methods depending on meteorological and flow conditions.

• If the initial impact of rain droplets dislodges soil, the phenomenon is called rainsplash erosion.
• If overland flow is directly responsible for sediment entrainment but does not form gullies, it is called "sheet erosion".
• If the flow and the substrate permit channelization, gullies may form; this is termed "gully erosion".

Key fluvial depositional environments[link]

The major fluvial (river and stream) environments for deposition of sediments include:

• Deltas (arguably an intermediate environment between fluvial and marine)
• Point bars
• Alluvial fans
• Braided rivers
• Oxbow lakes
• Levees
• Waterfalls

Aeolian processes: wind[link]

Wind results in the transportation of fine sediment and the formation of sand dune fields and soils from airborne dust.

Glacial processes[link]

Glacial sediments from Montana

Glaciers carry a wide range of sediment sizes, and deposit it in moraines.

Mass balance[link]

The overall balance between sediment in transport and sediment being deposited on the bed is given by the Exner equation. This expression states that the rate of increase in bed elevation due to deposition is proportional to the amount of sediment that falls out of the flow. This equation is important in that changes in the power of the flow changes the ability of the flow to carry sediment, and this is reflected in patterns of erosion and deposition observed throughout a stream. This can be localized, and simply due to small obstacles: examples are scour holes behind boulders, where flow accelerates, and deposition on the inside of meander bends. Erosion and deposition can also be regional: erosion can occur due to dam removal and base level fall. Deposition can occur due to dam emplacement that causes the river to pool, and deposit its entire load or due to base level rise.

Shores and shallow seas[link]

Seas, oceans and lakes accumulate sediment over time. The sediment could consist of terrigenous material, which originates on land, but may be deposited in either terrestrial, marine, or lacustrine (lake) environments; or of sediments (often biological) originating in the body of water. Terrigenous material is often supplied by nearby rivers and streams or reworked marine sediment (e.g. sand). In the mid-ocean, living organisms are primarily responsible for the sediment accumulation, their shells sinking to the ocean floor upon death.

Deposited sediments are the source of sedimentary rocks, which can contain fossils of the inhabitants of the body of water that were, upon death, covered by accumulating sediment. Lake bed sediments that have not solidified into rock can be used to determine past climatic conditions.

Key marine depositional environments[link]

Holocene eolianite and a carbonate beach on Long Island, Bahamas.

The major areas for deposition of sediments in the marine environment include:

• Littoral sands (e.g. beach sands, runoff river sands, coastal bars and spits, largely clastic with little faunal content)
• The continental shelf (silty clays, increasing marine faunal content).
• The shelf margin (low terrigenous supply, mostly calcareous faunal skeletons)
• The shelf slope (much more fine-grained silts and clays)
• Beds of estuaries with the resultant deposits called "bay mud".

One other depositional environment which is a mixture of fluvial and marine is the turbidite system, which is a major source of sediment to the deep sedimentary and abyssal basins as well as the deep oceanic trenches.

Any depression in a marine environment where sediments accumulate over time is known as a sediment trap.

The null point theory explains how sediment deposition (geology) undergoes a hydrodynamic sorting process within the marine environment leading to a seaward fining of sediment grain size.

Environmental issues[link]

Erosion and agricultural sediment delivery to rivers[link]

One cause of high sediment loads from slash and burn and shifting cultivation of tropical forests. When the ground surface is stripped of vegetation and then seared of all living organisms, the upper soils are vulnerable to both wind and water erosion. In a number of regions of the earth, entire sectors of a country have become erodible. For example, on the Madagascar high central plateau, which constitutes approximately ten percent of that country's land area, most of the land area is devegetated, and gullies have eroded into the underlying soil in furrows typically in excess of 50 meters deep and one kilometer wide.^{[citation needed]} This siltation results in discoloration of rivers to a dark red brown color and leads to fish kills.

Erosion is also an issue in areas of modern farming, where the removal of native vegetation for the cultivation and harvesting of a single type of crop has left the soil unsupported. Many of these regions are near rivers and drainages. Loss of soil due to erosion removes useful farmland, adds to sediment loads, and can help transport anthropogenic fertilizers into the river system, which leads to eutrophication.

Dregs[link]

Sediment in wine, beer, Turkish coffee or other beverages is known as dregs.

See also[link]

• Bar (river morphology)
• Beach cusps
• Biorhexistasy
• Bioswale
• Decantation
• Erosion
• Exner equation
• Particle size (grain size)
• Regolith
• Sand
• Sediment precipitation
• Sediment trap
• Sedimentary depositional environment
• Settling
• Surface runoff
• Deposition (geology)

References[link]

• Prothero, Donald R.; Schwab, Fred (1996), Sedimentary Geology: An Introduction to Sedimentary Rocks and Stratigraphy, W. H. Freeman, ISBN 0-7167-2726-9 
• Siever, Raymond (1988), Sand, New York: Scientific American Library, ISBN 0-7167-5021-X 
• Nichols, Gary (1999), Sedimentology & Stratigraphy, Malden, MA: Wiley-Blackwell, ISBN 0-632-03578-1 
• Cambridge, MA, H. G. (1978), Sedimentary Environments: Processes, Facies and Stratigraphy, Blackwell Science, ISBN 0-632-03627-3 

Laurie Spiegel (born September 20, 1945 in Chicago)^[1] is an American composer. She has worked at Bell Laboratories, in computer graphics, and is known primarily for her electronic-music compositions and her algorithmic composition software Music Mouse. She also plays the guitar and lute.^[2]

Spiegel was seen by some as a pioneer of the New York new-music scene. She withdrew from this scene in the early 1980s, believing that its focus had shifted from artistic process to product. While she continues to support herself through software development, Spiegel aims to use technology in music as a means of furthering her art rather than as an end in itself. In her words, "I automate whatever can be automated to be freer to focus on those aspects of music that can't be automated. The challenge is to figure out which is which."^[3]

Spiegel's realization of Johannes Kepler's "Harmonices Mundi" was chosen for the opening track on the "Sounds of Earth" section of the golden record placed on board the Voyager spacecraft in 1977.^[4] Her piece called "Sediment" was used in the "cornucopia scene" of the 2012 movie The Hunger Games.^[5]

Career[link]

Best known for her use of interactive and algorithmic logic as part of the compositional process, Spiegel worked with Buchla and Electronic Music Laboratories synthesizers and subsequently many early, often experimental and prototype-level music and image generation systems, including GROOVE system (1973-78), Alles Machine (1977) and Max Mathews's RTSked and John R.Pierce tunings (1984, later known as the Bohlen-Pierce scale) at Bell Labs, the alphaSyntauri for Apple II (1978-81), the McLeyvier (1981-85).^[6][4]

Spiegel's best known and most widely used software was "Music Mouse - An Intelligent Instrument" (1986) for Macintosh, Amiga and Atari computers.^[7][8] The "intelligent instrument" name refers to the program's built-in knowledge of chord and scale convention and stylistic constraints.^[9] Automating these processes allows the user to focus on other aspects of the music in real time.^[10] In addition to improvisations using this software, Spiegel composed several works for "Music Mouse", including "Cavis muris" in 1986, "Three Sonic Spaces" in 1989, and "Sound Zones" in 1990.^[4] She continued to update the program through Macintosh OS 9, and as of 2012, it remained available for purchase or demo download from her website.^[8]

In addition to electronics and computer-based music, Spiegel's opus includes works for piano, guitar and other solo instruments and small orchestra, as well as drawings, photography, video art, numerous writings and computer software.^[7] In the visual domain, Spiegel wrote one of the first "drawing" or "painting" programs at Bell Labs, which she expanded to include interactive video and synchronous audio output.

Pursuing her concept of "visual music", she was a Video Artist in Residence at The Experimental Television Lab at WNET/Thirteen in New York (1976).^[11] She composed series music for the TV Lab's weekly "VTR - Video and Television Review" and audio special effects for their 2-hour science fiction film The Lathe of Heaven, both under direction of David Loxton.^[12]

During the 1970s Spiegel supported herself by both teaching and soundtrack composition, having steady work at Spectra Films, Valkhn Films, the TV Lab and for various individual video artists, animators and film makers. Spiegel did much less accompanitive music in the 1980s, focusing on creating music software and consulting in the music technology field, as well as additional teaching at Cooper Union and NYU.^[7]

Education[link]

Spiegel's early musical experiences were largely self-directed, beginning with the mandolin, guitar, and banjo she had as a child, which she learned to play by ear.^[13] She taught herself Western music notation at the age of 20, after which she began writing down her compositions.^[14]

Spiegel attended Shimer College through the school's early entrance program, which allows students to enter college without having completed high school.^[15] She subsequently attended Oxford University, initially through Shimer's Oxford study abroad program, under which students spend a year continuing the Great Books core curriculum in Oxford while taking tutorials from Oxford.^[16][17]

After receiving her AB degree in the Social Sciences from Shimer in 1967,^[18] Spiegel stayed in Oxford an additional year,^[16] commuting to London to study guitar, theory and composition with John W. Duarte.^[18] After moving to New York, where she briefly worked in social sciences research and documentary film, she went on to study composition with Jacob Druckman and Vincent Persichetti at the Juilliard School from 1969 to 1972, privately with Emmanuel Ghent, then she relocated along with Druckman to Brooklyn College, completing her MA in Music Composition there in 1975.^[1]

Articles and interviews[link]

• Interview with Laurie Spiegel on Tokafi
• The Different Computer of Laurie Spiegel on radiom
• Rare ’70s Electronic Music Is Hidden in The Hunger Games on Wired

Discography[link]

• 60x60 (2006-2007) released 2008. A two-CD compilation of 60-second works from the 60x60 project.
• Ooppera, 2004. An album of 10-minute operas created from processed animal sounds.
• Harmonices Mundi (1977, released 2004). A realization of Kepler's vision of planetary motion.
• The P-ART Project - 12 Portraits, 2001. 12-composer compilation including Spiegel's "Conversational Paws".
• Obsolete Systems, 2001. A retrospective of Spiegel's work through the 70s and 80s, performed on currently-obsolete electronic instruments.
• OHM: The Early Gurus of Electronic Music, 2000. 3-CD compilation featuring Spiegel's 1974 Appalachian Grove.
• Miniatures 2 - a sequence of sixty tiny masterpieces, 2000. A sixty-artist compilation soundtrack to Dan Sandin's video A Volume of Julia Sets.
• Female of the Species, a 2-CD compilation of female experimental composers
• Enhanced Gravity, 1999. Compositions as well as text and multimedia art by Spiegel, also featuring multimedia art by 9 others.
• Cocks Crow, Dogs Bark: New Compositional Intentions, 1998. Companion CD to Leonardo Music Journal #7, featuring The Unquestioned Answer, described in that journal.
• Women in Electronic Music - 1977, 1977, re-released 1998. Compilation CD of women in electronic music.
• Computer Music Journal Sound Anthology, 1996. Companion CD to the 20th Anniversary Issue of Computer Music Journal
• Unseen Worlds, 1991, re-released 1994. Works by Laurie Spiegel.
• The Virtuoso in the Computer Age - III, 1993. Compilation CD of four electronic artists, featuring Spiegel's Cavis Muris (1986).
• Murmurs of Earth: The Voyager Interstellar Record, 1992. Music from Sounds of Earth produced to be sent up on the Voyager spacecraft, containing on excerpt of Harmonices Mundi.
• New American Music Vol. 2. Out of print LP.
• The Expanding Universe. Contains 4 pieces created using the GROOVE system at Bell Labs.
• Music for New Electronic Media, 1977. Early works by several electronic composers.

Works cited[link]

References[link]

External links[link]

• Laurie Spiegel's website
• Biography on Vox Novus
• Joanna Bosse, "Laurie Spiegel". Grove Music Online (subscription access).
• EMF Media: Laurie Spiegel, by Kyle Gann
• Interview from 1979, including complete versions of Patchwork, Waves, The Orient Express and Expanding Universe