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Wave Erosion and Marine Geology How waves behave How the sea modifies coastlines
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Waves
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Essential Points 1.Waves are created by the wind 2.Water in waves oscillates but does not move with the wave 3.What happens when waves hit the shore 4.Storm surges can be catastrophic How Waves Behave
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Wave Fetch
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The Highest Recorded Ocean Wave 1.Waves are created by the wind
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Global Wave Heights 1. Waves are created by the wind
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Freak 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 wind
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Wave 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 negligible 2. Water in a wave oscillates but does not move with the wave
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Wave Motions 2. Water in a wave oscillates but does not move with the wave
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When Waves Meet the Shore When the bottom interferes with wave motion, the wave steepens and the top overtakes the bottom. 3. What happens when waves hit the shore
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Wave Refraction Waves change path when they reach shallow water Wave energy is concentrated on headlands and spread out in bays 3. What happens when waves hit the shore
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Wave Refraction off Cape Cod 3. What happens when waves hit the shore
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Rips When waves break parallel to a beach, rips occur 3. What happens when waves hit the shore
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Rips, Lake Superior
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Oblique Rips 3. What happens when waves hit the shore
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Storm Waves: Galveston, Texas, September 8, 1900: 6000-8000 dead 3600 houses destroyed 4. Storm surges can be catastrophic
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Raising Galveston – 6 in. to 17 ft.
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“ A rickety maze such as Dr. Seuss might have drawn ”
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The Lift in Progress
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Pumping in the Sand 4. Storm surges can be catastrophic
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The Galveston Seawall 4. Storm surges can be catastrophic
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Essential Points 1.Waves are created by the wind 2.Water in waves oscillates but does not move with the wave 3.What happens when waves hit the shore 4.Storm surges can be catastrophic How Waves Behave
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How the sea modifies coastlines
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Essential Points 1.Wave Action erodes or deposits material along coastlines 2.Types of coastline 3.Deltas are governed by deposition, waves, and tides 4.Reefs are a special type of coastline in tropical regions 5.Global sea level is affected by ice ages and plate tectonics How the sea modifies coastlines
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In 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 coastlines
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Property 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 left 1. Wave Action erodes or deposits material along coastlines
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Marine Erosion Chemical Attack Abrasion Wave Impact Compressed Air Backwash 1. Wave Action erodes or deposits material along coastlines
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Water Velocity and Erosion 1. Wave Action erodes or deposits material along coastlines
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Longshore 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 Drift 1. Wave Action erodes or deposits material along coastlines
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Beach Drift, New Jersey
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Types of Coast Degree 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 coastline
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Effects 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 common 2. Types of coastline
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Secondary Coasts Are Modified by Marine Erosion or Deposition
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Secondary Coasts Erosion 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 Bar 2. Types of coastline
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Primary Coastlines Are Very Common Drowned River Valleys (Estuaries) Drowned Glacial Valleys (Fiords) 2. Types of coastline
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Estuaries, Chesapeake Bay
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Tidal Marshes, Chesapeake Bay 2. Types of coastline
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Fiord Coast, Labrador
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Other Ways Primary Coasts Can Form Deltas Volcanic Activity Uplift 2. Types of coastline
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Primary and Secondary Coastlines 2. Types of coastline
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Baymouth Bar, Michigan
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Wave-Cut Platform, California Footer
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Coastal Terraces, California
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Sea Stacks, Washington
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Former Stack, Michigan
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Sea Caves, Apostle Islands
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Wave-Cut Arch, Lake Superior
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Delta Coasts Deposition-Dominated Wave Dominated Tide-Dominated 3. Deltas are governed by deposition, waves, and tides
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The Mississippi – A Deposition- Dominated Delta 3. Deltas are governed by deposition, waves, and tides
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Yukon and Nile Deltas – Balance of Deposition and Wave Action 3. Deltas are governed by deposition, waves, and tides
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Sao Francisco, Brazil – A Wave- Dominated Delta
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Ganges, Bangladesh – A Tide- Dominated Delta
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Reefs Are a Major Type of Coast in Tropical Areas 4. Reefs are a special type of coastline in tropical regions
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Fringing Reef, Tahiti
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Tarawa – A Typical Atoll 4. Reefs are a special type of coastline in tropical regions
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Reefs Also Form along the Edges of Large Islands and Continents These Are Barrier Reefs Australia Yucatan Belize West Florida and the Keys 4. Reefs are a special type of coastline in tropical regions
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Sea Level and Tectonic Activity 5. Global sea level is affected by ice ages and plate tectonics
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Depth of Ocean Crust 5. Global sea level is affected by ice ages and plate tectonics
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Sea-Floor Spreading and Sea Level 5. Global sea level is affected by ice ages and plate tectonics
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Sea Level and Tectonic Activity 5. Global sea level is affected by ice ages and plate tectonics
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Essential Points 1.Wave Action erodes or deposits material along coastlines 2.Types of coastline 3.Deltas are governed by deposition, waves, and tides 4.Reefs are a special type of coastline in tropical regions 5.Global sea level is affected by ice ages and plate tectonics How the sea modifies coastlines
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