Coastlines.pptx

coast

1. Coastlines

2. Classifying Coasts Coasts can be classified by a method that takes into account tectonic position and sea level. Primary coasts Secondary coasts

3. Primary coasts Primary coasts are young coasts dominated by terrestrial influences. Land erosion coasts Coasts built out by land processes Volcanic coasts Coasts shaped by earth movements

4. Secondary coasts Secondary coasts are older coasts that have been changed by marine influence. Waves and currents Stream erosion Abrasion of wind-driven particles Freeze/thaw cycles Slumping

5. Primary Coasts

6. © 2002 Brooks/Cole, a division of Thomson Learning, Inc. Secondary Coasts Waves are one of the forces that shape secondary coasts.

7. © 2002 Brooks/Cole, a division of Thomson Learning, Inc. Large Scale Features of Secondary Coasts These features are associated with secondary coasts.

8. Beaches A beach is a geological landform along the shoreline of a body of water. It usually consists of loose particles which are often composed of rock, such as sand, gravel, pebbles , or cobble . A beach is a zone of loose particles that covers a shore.

9. Coastal Water Movement Breaking waves provide the energy that changes the shape and texture of the beach deposits. As waves shoal (trough bottom) in shallow water celerity decreases, wavelength decreases, wave height increases, waves become less stable and refraction occurs. Refraction is the bending of waves towards shallower water so that they break almost parallel to the shore. Waves become unstable and break in very shallow water.

10. The beach is the part of the land that touches the sea. It can be divided into the: Off shore, Near shore (breaker zone, surf zone, swash zone), and the Back Shore Position of the divisions of the beach varies with the tides, advancing landward with high tide and retreating seaward with low tide.

11. Marina beach

12. Goa beach

13. Dubai

14. Phunket beach

15. Malaysia

16. Punalu'u Beach is the most visited of the few black sand beaches on Hawaii's Big Island and the stunningly black sand is actually volcanic rock, deposited as lava and subsequently cooled when met by the ocean. Apparently to take any of the sand home would result in you being cursed by a volcano goddess by the name of Pele.

17. One of only 2 green sand beaches in the world, the truly magnificent sight of Papakolea Beach can be experienced by travelling to Hawaii's Ka'u district. Again , the unique colour of its sand can be attributed to volcanic activity - specifically, the green hue belongs to the abundance of olivine crystals which have been produced as a result of a nearby cinder cone erupting and eroding.

18. You may need to wear your shades when visiting Hyams Beach in New South Wales, Australia, but not just due to the sun. It's not surprising after looking at photos but this sublime stretch of beach is home to the whitest sand in the world, an honour awarded by the Guinness Book of Records.

19. The hills surrounding Pfeiffer Beach in Big Sur, California, are rich in Manganese Garnet. A result of this being washed down onto the beach is the colour scheme you can see above - the entire stretch of sand has become a shifting, pink and purple canvas. Although it's probably inedible, I can't help picturing a bowl of Raspberry Ripple ice-cream every time I see it.

20. You won't find many beaches elsewhere in the world with sand as red as this one. Kaihalulu , or Red Sand Beach, is situated on the island of Maui and can thank the neighboring cinderc one hill for its intensely deep red appearance.

21. Waves generate longshore currents that flow parallel to the beach and rip currents that flow perpendicularly to the beach. Angle of wave approach is the acute angle (less than 90 o ) between the wave crest and the beach. The direction of longshore current varies with the direction of wave approach.

22. Rip current Long shore currents can also be generated by wave set-up. Where two opposing long shore currents collide, they form a swift, narrow, seaward rip current.

23. Beach sediments are moved by currents and waves, especially breakers. A beach profile is a cross section of the beach along a line that is perpendicular to the shoreline. A swell profile is concave upward with a wide, broad berm (relatively flat backshore) and steep intertidal beach face. A storm profile displays erosion of the berm and a broad flat intertidal beach face. A sand budget is the balance between sediment added to and sediment eroded from the beach.

24. S and Budget

25. Sections of coast in which sand input and sand output are balanced are referred to as coastal cells. Coastal Cells

26. Coastal Dunes Sand dunes are formed by winds blowing sand landward from the dry part of the beach. Well developed dunes typically have a sinusoidal profile with the primary dune at the landward edge of the beach and possible secondary dunes located farther inland. Vegetation on the dunes traps windblown sand on their downwind side and promotes dune growth and stability.

27. Blowouts are wind-scoured breaks in the dune or depressions in the dune ridge and commonly occur if vegetation is destroyed . Strong and persistent, the tidal range is large and the beach is wide and gently sloping. Sand saltates (bounces) up the windward side of the dune, collects in the wind-shadow at the top and periodically slides down the leeward face of the dune when the accumulation of sand becomes over-steepened—resulting in dune migration.

28. Wave erosion of sand dunes transports sand offshore and creates a steep scarp at the base of the dune. Dunes act as a natural barrier and prevent inland flooding. Human activity that damages vegetation leads to dune destruction by blowouts and wash over by storm waves.

29. Barrier Islands Barrier islands are islands composed of sediment that parallel the coast and form where sand supply is abundant and a broad sea floor slopes gently seaward. The islands are separated from the mainland by shallow bodies of water which are connected to the ocean through tidal inlets.

30. A series of distinct environments develop across the island parallel the beach and include the nearshore zone, dune field, back-island flats and salt marshes. Barrier islands are created in many ways including: sand ridges isolated by rising sea level, Sand spits breached during a storm, vertical growth and emergence of longshore sand bars. As sea level rises, barrier islands migrate landward as washover transports sediments from the seaward side of the island to the landward side.

31. Cliffed Coasts A sea cliff is an abrupt rise of the land from sea level. A sea cliff is most vulnerable to erosion at its base because waves that slam against the cliff compress air inside cracks which expands violently, sediment is hurled against the cliff by the waves, and sea water dissolve some rock types. When sufficient rock at the base of the cliff has been removed, the upper part of the cliff collapses. Collapsed material protects the base of the sea cliff from additional erosion until it is destroyed and removed.

32. Rate at which the cliff recedes is dependent upon: Composition and durability of cliff material. Joints, fractures, faults and other weaknesses in the cliff material. Amount of precipitation. Steepness of the cliff. The wave-cut platform is the gentle sloping area in front of the sea cliff that was produced by sea-cliff retreat.

33. Deltas A delta is an emergent accumulation of sediment deposited at the mouth of a river as it flows into a standing body of water. Deltas were named after the Greek letter delta  . The three major areas of a delta are delta plain ,delta front and prodelta . In cross section, a delta’s deposits can be divided into three sets of beds: topset beds, foreset beds, and bottomset beds.

34. As sediment accumulates the delta expands seaward with foreset beds burying bottomset beds and topset beds covering foreset beds. Shape of the delta can be altered by tides, waves and river deposition. Reduction in the supply of sediment to a delta results in delta erosion and subsidence as the sediments of the delta compact.

35. Types of coastal setting The term coast has a much broader meaning than shoreline and includes many other habitats and ecosystems associated with terrestrial and marine processes. Shorelines are one of the most productive ecosystems and because they are shallow, they strongly respond to the effects of waves, tides and weather.

36. The six major coastal settings are: Estuary, Lagoon, Salt marsh, Mangrove swamp and Coral reef.