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Sediments - Sediments Sediment is particles of organic or...

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Sediments Sediment is particles of organic or inorganic matter that accumulate in a loose, unconsolidated form. Sediment may be classified by grain size or by the origin of the majority of the particles.
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Ocean sediments are important because they provide A record of ocean basin history. A record of global climate change. A record of bottom physical processes (bottom currents, etc.)
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Seismic echo profile of sea floor sediments in the Gulf of Mexico
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A deep-sea sediment core obtained by the drilling ship Glomar Challenger
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Cores are sectioned longitudinally, placed in trays, and stored in hermetically sealed cold rooms. The Gulf Coast Repository of the Ocean Drilling Program, located at Texas A&M University (pictured here), stores about 75,000 sections taken from more than 80 kilometers (50 miles) of cores recovered from the Pacific and Indian oceans. Smaller core libraries are maintained at the Scripps Institution in California (Pacific and Indian oceans) and at the Lamont Doherty Earth Observatory in New York State (Atlantic Ocean). Sediment cores in storage
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Classification of sediments by particle size Although boulders, cobbles, and peddles occur in the ocean, most marine sediments are made of finer particles: sand, silt, and clay.
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Current profile near the bottom. If the bottom current is strong, it can move the bottom sediments. increasing height above the bed, Z increasing current velocity, u Water flowing near a solid surface is slowed down by friction along the boundary, and the region of flow influenced by proximity to the surface is called the boundary layer . A boundary layer develops wherever a fluid moves over a surface, whether it be water over the sea- bed, winds over the sea- surface, or syrup over a tabletop. A velocity gradient a change of velocity with depth exists near the boundary
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The velocities of currents required for erosion The velocities of currents required for erosion, transportation, and deposition (sedimentation) of sediment particles of different sizes. To dislodge and carry a particle of size A, the speed of a current must exceed 20 cm/s. When the current falls below 1 cm/s, the particle will be deposited. For sand-size and coarser grain sediments, the larger the particle, the stronger the current must be to erode the material. Surprisingly, greater current velocities are required to erode clays (finer sediments), despite their small size, than to erode fine sand. Those fine- particle clays tend to form aggregates thus are cohesive and, hence, "stickier" than sand.
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Sediments of high(top) and low(bottom) energy environments
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Well-sorted sediments : * Composed of particles of mostly one size.
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