test2 - UNIT 5 SEDIMENTS MAIN CONCEPTS TO LEARN How...

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UNIT 5: SEDIMENTS MAIN CONCEPTS TO LEARN How sediments are classified (by size and source). Sediment can be classified by particle size. Waves and currents generally transport smaller particles farther than larger particles. 1. How sediments are classified (by size and source) and where they are derived Terrigenous: Erosion of land, volcanic eruptions, blown dust. Mostly the size of sand (<2mm), easily transported across the continental shelf, settle on the deepest ocean floor. ~45% Biogenous: Organic, accumulation of hard parts of some marine organisms. Oozes settle straight down. ~55% Hydrogenous: Precipitation of dissolved minerals. (Manganese nodules, Phosphorite deposits). <1% Cosmogenous: Dust from space, meteorite debris. (0.2mm – 0.8mm). 0% The distribution of sediments, factors controlling the occurrence of terrigenous, biogenous, and hydrogenous sediments. Also contains biogenous sediments which dissolve the terrigenous sediments because of high biological productivity in coastal water and the presence of skeletal remains of living organisms on bottom or in the water above. Hydrogenous sediments - originate from chemical reactions that occur in the existing sediment, e.g. Manganese nodules, Evaporites Relationship among erosion, transport and deposition depends on particle size and current velocity. The velocities of currents vs.erosion rates of sediments. Note how weaker currents can move smaller particles of sediment, while stronger currents are needed to erode larger sediment. Especially, factors controlling the occurrence of calcium carbonate sediments and oozes. Ooze is classified by the type of life form from which it is derived. Calcareous ooze is formed by organisms, such as foraminifera, which contain calcium carbonate in their shells or skeletons. Siliceous ooze is formed by organisms that contain silica in their shells. Diatoms are one type of organism whose remains contribute to siliceous ooze. Calcareous compounds were either deposited in the oceans by rivers, or dissolved at mid-ocean ridges. Plants and animals ate the compounds and formed shells and skeletons. After the death of their owners, the sediments fall to the bottom.
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Sources of terrigenous, biogenous, and hydrogenous sediments. Hydrogenous sediments are usually the result of chemical reactions. Hydrogenous sediments are often found in the form of nodules containing manganese and iron oxides. Terrigenous sediments, the most abundant, originate on continents or islands near them. Biogenous sediments are composed of the remains of once-living organisms. Hydrogenous sediments are precipitated directly from seawater. Cosmogenous sediments, the ocean's rarest, come to the seabed from space. How oceanic sediments are collected and studied; importance of ocean sediments
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This note was uploaded on 04/07/2008 for the course ISNS 3367 taught by Professor Pujana during the Spring '08 term at University of Texas at Dallas, Richardson.

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test2 - UNIT 5 SEDIMENTS MAIN CONCEPTS TO LEARN How...

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