6.sealevelmechanisms

6.sealevelmechanisms - Pre-show Mechanisms for sea level...

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View of NY harbor an ice-free world (73 m rise) 80 Ma Cretaceous North America Mechanisms for sea level change 20,000 year ago eastern U.S. Shoreline Gimme Shelter! Oh, a storm is threat'ning My very life today If I don't get some shelter Oh yeah, I'm gonna fade away
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Sea-Level Measurements Satellite altimetry back to 1993 Tide gauges back to 1850 Coastal sediments back to 20,000 years ago Reef terraces back to 130,000 years ago Sequence stratigraphy back to 1,000,000,000+ y ears ago instruments / modern rock record / ancient Pre-anthropogenic Geology needed to evaluate natural, pre-anthropogenic sea-level
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Definitions and Mechanisms
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transgression: movement of the beach landward that usually occurs during sea-level rise regression: movement of the beach seaward Surf City Shipbottom Transgressions & Regressions
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Processes effecting sedimentary record of sea level change eustasy (= global sea level change) “tectonics” = subsidence/uplift, loading, compaction, flexural effects sediment supply
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Rise/fall of sea level relative to the center of the Earth Eustasy = global sea-level Eduard Suess in 1888 Justice Stewart: can’t define it…”but know it when I see it” Eustasy = Ecstasy Eustasy was first used by Clarence Dutton in 1889 who first spelled this as eustacy but when it was realized that Greek had no “c” the spelling of the word was changed to eustasy. Hallam (1984) drives this etymological point home by pointing out that out ecstasy has no ‘c’ either.
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Posamentier et al., 1988 relative sea level change with respect to earth's crust Relative sea level caused by eustasy and subsidence/uplift best example, Mississippi Delta, undergoing rapid relative sea level rise due to subsidence (10 mm/yr), yet global sea level is slowly rising Relative sea level = eustasy + subsidence
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transgression: movement beach landward regression: movement of the beach seawar d Function of eustasy, subsidence, sediment supply Caused by relative sea-level changes or sediment supply e.g., regression during relative a sea-level rise Transgressions & regressions
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Regional Mississippi Delta Relative sea level rapidly rising loading subsidence, eustasy Local Atchafalaya Bay: transgression Near river mouth (until Army Corp. dammed river): Regression Regression during sea-level rise
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Clicker question: definitions A) A mortal sin B) Movement of the beach landward C) Movement of the beach seaward D) Unrelated to sea level or sediment supply E) Always caused by a relative rise What is a transgression?
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Clicker question: definitions A) Ecstasy B) Global sea level rise C) Hard to define D) Sea level rise relative to center of Earth E) All of the above What is a eustasy?
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Clicker question: definition A. Movement of the beach landward B. Caused by transgression C. Caused by eustatic rise and/or subsidence D. Movement of the beach seaward E. Cousin Irv’s beach house is flooded What is a relative sea level rise?
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6.sealevelmechanisms - Pre-show Mechanisms for sea level...

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