The Work of Waves and Wind
اسلاید 1: The Work of Waves and WindObjectives:Explain the characteristics of ocean waves and tidesPresent coastline features of erosion, transport and depositionExamine the processes of wind erosion and depositionDifferentiate different types of duneDescribe the wind deposit LOESS
اسلاید 2: wave lengthwave heightcresttroughparticles in waves follow a circular patternCOASTAL LANDFORMS
اسلاید 3: At the shorelineWater becomes shallow, wave height increases because wave length decreasesWaves become steeper, then collapse (breakers)
اسلاید 4: Surf - sequence of breaking wavesSwash - water sliding up beachBackwash - water flowing back down beach to sea
اسلاید 5: Wave refractionClose to coast, water gets more shallowWaves are slowed downIf waves arrive at an angle, one part is slower than the restCauses waves to bend = wave refraction
اسلاید 6: Wave refraction BayHeadland
اسلاید 7: Waves arriving at bays are slow (deposition)At headlands, faster (erosion)
اسلاید 8: A sequence of features is produced as headlands are degraded Sea cliffsWaves erode base -undercuttingthe cliff retreats
اسلاید 9: Also produces sea caves As cliffs retreat produces a wave-cut platform
اسلاید 10: Headlands may be eroded back leaving a remnant (stack)stack
اسلاید 11: Longshore driftWaves arrive at a coast at an angle (swash)Backwash returns at 90 degreesSand is moved along the beach = longshore drift or longshore current
اسلاید 12: Coastal deposition Result of longshore drift and a lot of sediment= produces extensions of deposit from the shoreline
اسلاید 13: May grow across a bay (baymouth bar)May link an island to the main land (tombolo)spit = curved extension
اسلاید 14: TIDES Daily changes in sea levels Tides rise (FLOOD) to produce a HIGH TIDE And fall (EBB) (LOW TIDE) Produced by the gravitational pull that the Sun and Moon exert on the Earth’s surface (including the oceans)Moon/Sun
اسلاید 15: This side is pulled towards the Sun and/or Moon by gravitational attractionThis side bulges out because of inertiaTherefore, there are two high tides on Earth at any one time
اسلاید 16: Every 24 hours 50 minutes any point on the Earth rotates through two bulgesEach location experiences 2 high (FLOOD) tides and 2 low (EBB) tides
اسلاید 17: Types of CoastlineSubmergence and emergence changes coastlinesPocket beaches
اسلاید 18: Emergent coast Uplifted land surfaceCoastal landforms are found above present sea levela wave-cut platform when elevated - uplifted marine terrace
اسلاید 19: Submergent coast Rise in sea levelSubmergent coast Landforms under waterA ria coastline is an example of submergence
اسلاید 20: Submergence ShorlinesRia coast - shorline valleys eroded by rivers are submergedhas many offshore islandsexposure to waves erodes islands and headlandsFiord coast - shoreline valleys created by glaciers are submergedvalleys are deep and straightbecause of the depth, there are few beaches
اسلاید 21: Barrier Island CoastsOccur on low lying coasts with gentle gradientsBARRIER ISLANDS - low ridges of sand built by wavesbehind the islands are lagoonsshallow water with tidal depositsTIDAL INLETS - gaps between the islands
اسلاید 22: Delta and Volcano CoastsDELTA - deposit by rivers entering the seaWater slows down and spreads out as it enters Channel divides and subdivides to create DISTRIBUTARIESVolcano coasts develop in volcanic depositsLow cliffs form in fresh lava
اسلاید 23: Coral reefsCorals build up calcium deposits to produce reefsTo grow, corals need: Clear, warm, shallow water Wave actionCorbis Digital Stock
اسلاید 24: Coral reefs Fringing reef - directly attached to an island or coastBarrier reef - lagoon between coast and reefAtoll reef - circular reef surrounding a lagoon (no land in centre)
اسلاید 25: AEOLIAN (Eolian) LANDSCAPESWind erosion, transport and depositionOccurs in dry regions, with little vegetation such as deserts and coastal landscapes
اسلاید 26: Wind ErosionFaster the air flows, more erosion Erodes more rapidly if wind blows constantly from one direction2 TYPES OF WIND EROSIONABRASION and DEFLATION
اسلاید 27: DEFLATION HOLLOWS Removal of fine particles by wind leaves hollows behind (DEFLATION HOLLOWS)Also leaves a surface of closely packed stones (DESERT PAVEMENT)
اسلاید 28: WIND TRANSPORTATION- Very fine material may be carried in suspension in the air- But larger particles may be moved by 2 methods:SURFACE CREEP &SALTATION
اسلاید 29: 1.) SURFACE CREEP- material is rolled along the surface- accounts for 20% of wind transport
اسلاید 30: 2.) SALTATION- The asymmetrical bouncing of sand grains - Accounts for 80% of wind transport- Cause of shifting sand dunes
اسلاید 31: Aggradational land formsSAND SEAS (ERGS) = only 25% of the worlds desertssurface may be covered in RIPPLES
اسلاید 32: SAND DUNESare ridges of wind deposited sand- Usually 3 to 15 metres high, but can reach 180 metres- A continuously changing dune is ACTIVECorbis Digital Stock
اسلاید 33: The formation of dunes depends on:- amount of sand- speed and direction of wind- occurrence of vegetationCorbis Digital Stock
اسلاید 34: wind directionBACKSLOPESLIPFACEmovement of sandangle of reposecrest
اسلاید 35: TYPES OF SAND DUNE1.) BARCHAN- most common type- crescent-shapedWind directionbackslopeslip face
اسلاید 36: 2.) PARABOLIC DUNES- crescent-shaped but with the concave side on the windward side- usually elongated- may develop in associated with deflation hollowsWind direction
اسلاید 37: 3.) TRANSVERSE DUNES low sand ridge at right angles to the wind direction may form because of large amounts of sandwind
اسلاید 38: 4.) LONGITUDINAL DUNES low sand ridges parallel to the wind direction may form because of a limited amount of sand also known as seif duneswind
اسلاید 39: LOESSFinely textured sediment wind-blown long distancesWind-blown glacial debris formed large deposits
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