sp02u4p2 - Unit Four Deep-Sea Sediment Coring Unit IV...

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Unit Four Deep-Sea Sediment Coring ©Project Oceanography Spring 2002 99 Unit IV Deep-Sea Sediment Coring On the cutting edge… Cindy Pilskaln is on the cutting edge of science using the latest technology to study the sediments that make up the deep-sea floor. Using various types of core sampling devices, she is able to collect undisturbed layers of sediment. When these sediments are carefully analyzed, they tell a story about the formation of the ocean bottom that can be related to global events. Dr. Pilskaln hopes to continue her research and learn more about the biological and chemical processes that contribute to sediment deposition on the ocean bottom. The Story of Deep-Sea Sediments Lesson Objectives: Students will be able to do the following: Describe two ways to classify ocean floor sediments Compare and contrast three sediment sampling devices Explain how sediments can be used to create a historical record Key concepts: weathering, terrigenous sediment, biogenic sediment, core samplers, marine snow, chemical precipitates Formation of Deep-Sea Sediments The deep-sea ocean floor is made up of sediment . This sediment is composed of tiny particles such as fine sand, silt, clay, or animal skeletons that have settled on the ocean bottom. Over long periods of time, some of these particles become compressed and form stratified layers. Scientists that study these layers look at particle size, particle composition, and origin to help them create historical records of the deep ocean floor. Particle or grain size is determined by measuring the diameters of the particles in millimeters (mm) or microns (=1/1000 of a millimeter). The particles from largest to smallest are gravel, sand, silt, and clay. Gravel can be as big as a boulder ( > 256 mm) or as small as a granule (2-4 mm). Silt (0.00039-0.0625mm) and clay (0.0002-0.0039mm) are very tiny particles that are generally mixed together to form mud. Most deep ocean sediments are silt and mud. Most sediments form as rocks are broken down into smaller particles such as sand and clay. This process is
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Unit Four Deep-Sea Sediment Coring ©Project Oceanography Spring 2002 100 called weathering . Weathering can be either mechanical or chemical. Mechanical weathering can occur as ice, wind, or water wears away the rock’s surface. Chemical weathering can occur as rocks are dissolved by a chemical such as acid rain. The particles created as a result of weathering are called terrigenous sediments. These particles are transported to the ocean by wind and by rivers and streams. Once the particles enter the ocean, they are dispersed by waves, currents , and tides . The heaviest and largest particles that reach the oceans, such as sand, settle very quickly to the bottom as a result of gravity. Sand is deposited near the coast whereas the smaller silt and clay particles are transported farther distances offshore before they settle to the bottom. Often, large deposits of sand and silt pile up at the edge of
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This note was uploaded on 07/31/2011 for the course OCB 6050 taught by Professor Staff during the Spring '11 term at University of South Florida - Tampa.

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sp02u4p2 - Unit Four Deep-Sea Sediment Coring Unit IV...

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