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Wave Erosion and Marine GeologyWavesEssential PointsWave FetchSlide 5The Highest Recorded Ocean WaveGlobal Wave HeightsFreak WavesWave MotionsSlide 10When Waves Meet the ShoreWave RefractionWave Refraction off Cape CodRipsRips, Lake SuperiorOblique RipsStorm Waves: Galveston, Texas, September 8, 1900:Raising Galveston – 6 in. to 17 ft.“A rickety maze such as Dr. Seuss might have drawn”The Lift in ProgressPumping in the SandThe Galveston SeawallSlide 23How the sea modifies coastlinesSlide 25In the long run, nothing is as futile as trying to resist shoreline change.Property Values and Shoreline ErosionMarine ErosionWater Velocity and ErosionLongshore and Beach DriftBeach Drift, New JerseyTypes of CoastEffects of the PleistoceneSecondary Coasts Are Modified by Marine Erosion or DepositionSecondary CoastsPrimary Coastlines Are Very CommonEstuaries, Chesapeake BayTidal Marshes, Chesapeake BayFiord Coast, LabradorOther Ways Primary Coasts Can FormPrimary and Secondary CoastlinesBaymouth Bar, MichiganWave-Cut Platform, CaliforniaCoastal Terraces, CaliforniaSea Stacks, WashingtonFormer Stack, MichiganSea Caves, Apostle IslandsWave-Cut Arch, Lake SuperiorDelta CoastsThe Mississippi – A Deposition-Dominated DeltaYukon and Nile Deltas – Balance of Deposition and Wave ActionSao Francisco, Brazil – A Wave-Dominated DeltaGanges, Bangladesh – A Tide-Dominated DeltaReefs Are a Major Type of Coast in Tropical AreasFringing Reef, TahitiTarawa – A Typical AtollReefs Also Form along the Edges of Large Islands and ContinentsSea Level and Tectonic ActivityDepth of Ocean CrustSea-Floor Spreading and Sea LevelSlide 61Slide 62Wave Erosion and Marine Geology How waves behaveHow the sea modifies coastlinesWavesEssential Points1. Waves are created by the wind2. Water in waves oscillates but does not move with the wave3. What happens when waves hit the shore4. Storm surges can be catastrophicHow Waves BehaveWave FetchWave FetchThe Highest Recorded Ocean Wave1. Waves are created by the windGlobal Wave Heights1. Waves are created by the windFreak Waves •Addition of waves of different frequencies•Theoretically could reach 200 feet in Gulf of Alaska•One nearly sank the Queen Mary in WWII, with 15,000 troops aboard.1. Waves are created by the windWave Motions•Particles in a wave travel circular paths•The water in a deep-water wave does not move forward•Below wave base, wave effects are negligible2. Water in a wave oscillates but does not move with the waveWave Motions2. Water in a wave oscillates but does not move with the waveWhen Waves Meet the ShoreWhen the bottom interferes with wave motion, the wave steepens and the top overtakes the bottom.3. What happens when waves hit the shoreWave Refraction•Waves change path when they reach shallow water•Wave energy is concentrated on headlands and spread out in bays3. What happens when waves hit the shoreWave Refraction off Cape Cod3. What happens when waves hit the shoreRips•When waves break parallel to a beach, rips occur3. What happens when waves hit the shoreRips, Lake SuperiorOblique Rips3. What happens when waves hit the shoreStorm Waves: Galveston, Texas, September 8, 1900:•6000-8000 dead•3600 houses destroyed4. Storm surges can be catastrophicRaising Galveston – 6 in. to 17 ft.“A rickety maze such as Dr. Seuss might have drawn”The Lift in ProgressPumping in the Sand4. Storm surges can be catastrophicThe Galveston Seawall4. Storm surges can be catastrophicEssential Points1. Waves are created by the wind2. Water in waves oscillates but does not move with the wave3. What happens when waves hit the shore4. Storm surges can be catastrophicHow Waves BehaveHow the sea modifies coastlinesEssential Points1. Wave Action erodes or deposits material along coastlines2. Types of coastline3. Deltas are governed by deposition, waves, and tides4. Reefs are a special type of coastline in tropical regions5. Global sea level is affected by ice ages and plate tectonicsHow the sea modifies coastlinesIn the long run, nothing is as futile as trying to resist shoreline change.Change can be resisted for a while, but when the water wants something badly enough, it will come in and take it. 1. Wave Action erodes or deposits material along coastlinesProperty Values and Shoreline Erosion•If more than half the original lot is left, it’s Location, Location, Location•After that, it becomes obvious there soon won’t be any location left1. Wave Action erodes or deposits material along coastlinesMarine Erosion•Chemical Attack •Abrasion •Wave Impact •Compressed Air •Backwash1. Wave Action erodes or deposits material along coastlinesWater Velocity and Erosion1. Wave Action erodes or deposits material along coastlinesLongshore and Beach Drift•Most Beach Sand Is Created by Weathering and Carried to Coasts by Rivers•Beach Sand Moves along the Coast by Longshore and Beach Drift1. Wave Action erodes or deposits material along coastlinesBeach Drift, New JerseyTypes of CoastDegree of Modification•Primary - Not Modified Much by Wave Action•Secondary - Highly Modified by Wave Action History•Emergent - Land Rises or Water Level Falls•Submergent - Land Sinks or Water Level Rises Dominant Process•Erosional•Depositional 2. Types of coastlineEffects of the Pleistocene•Sea level has risen at least 100 meters in the last 18,000 years•Most coastlines globally are submergent•Primary coastlines are very common2. Types of coastlineSecondary Coasts Are Modified by Marine Erosion or DepositionSecondary CoastsErosion•Stack •Terraces •Tombolo •Erosion rate becomes very slow – wave energy dissipated crossing the wave-cut terrace. –Cliffs become higher, meaning more material to move. Deposition•Spit •Lagoon •Baymouth Bar •Barrier Bar2. Types of coastlinePrimary Coastlines Are Very Common •Drowned River Valleys (Estuaries) •Drowned Glacial Valleys (Fiords) 2. Types of coastlineEstuaries, Chesapeake BayTidal Marshes, Chesapeake Bay2. Types of coastlineFiord Coast, LabradorOther Ways Primary Coasts Can Form•Deltas •Volcanic Activity •Uplift 2. Types of coastlinePrimary and Secondary Coastlines2. Types of coastlineBaymouth Bar, MichiganWave-Cut Platform, CaliforniaFooterCoastal Terraces, CaliforniaSea Stacks, WashingtonFormer Stack, MichiganSea Caves, Apostle IslandsWave-Cut Arch, Lake SuperiorDelta Coasts•Deposition-Dominated•Wave Dominated•Tide-Dominated3. Deltas are governed by deposition, waves, and


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UWGB EARTH SC 102 - Wave Erosion and Marine Geology

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