Coasts

1. Coasts Areas where the land meets the sea…..

2. A shore (or shoreline) is the place where the land meets water (between low tide line and high tide line), but a coast includes a larger zone affected by this boundary. A beach is a zone of loose sediment that covers part or all of a shore on a depositional coast.

3. Coastal Regions/Zones • Seaward – toward the sea/ocean • Inland – toward the land

4. Coastal Regions/Zones • Foreshore – seaward of the berm crest; active zone of the beach. Extends from beach scarp to low tide mark. • (berm crest = highest point on the beach) • (beach scarp = high tide line) • Backshore – inland of the berm crest, extending to the farthest point where beach sand had been deposited

5. Coastal Regions/Zones • Nearshore – area of breaking waves • Offshore – area beyond breaking waves

6. Coastal Regions/Zones • Beach • Coast • Shore • Nearshore • Offshore • Backshore • Foreshore

7. Coastal Regions/Zones • Beach • Coast • Shore • Nearshore • Offshore • Backshore • Foreshore

8. Classifying Coasts Coasts are influenced by many factors. It is most useful to classify coasts based on predominant events that occur there, such as: • Erosion • Deposition

9. Classifying Coasts Another way to classify coasts is by tectonic activity. • Active (active margin) • Passive (passive margin)

10. Classifying Coasts A third way to classify coasts is by what is influencing or shaping them: either land processes or marine processes • Primary (land processes) • Secondary (marine processes)

11. Classifying Coasts The last way we can classify coasts is by changes in sea level. • Emergent Coast • Submergent Coast

12. Erosional Coasts

13. The Twelve Apostles - sea stacks along the southern coast of Australia – are part of an erosional coast.

14. Erosional Coastlines • Well-developed cliffs • Recent tectonic activity (active margins) • Wave erosion increases with • More shore exposed to open ocean • Smaller tidal range • Weaker bedrock

15. Features of Erosional Coastlines • Headlands – areas of the shore that stick out farther than others

16. Features of Erosional Coastlines Wave-cut cliff (sea cliffs) – slope abruptly from land into the ocean; usually formed from the collapse of undercut notches

17. Features of Erosional Coastlines Wave-cut platform– smooth, nearly level terrace just offshore, marking the submerged limit of rapid marine erosion. Created by wave action

19. Features of Erosional Coastlines Sea cave – cave formed by wave action in zones of weakness in sea cliffs

20. Features of Erosional Coastlines Sea arches - a natural opening eroded out of a cliff face by marine processes

21. Features of Erosional Coastlines Sea stacks - steep column or columns of rock in the sea near a coast formed by wave action

23. Features of Erosional Coastlines http://www.oceanfootage.com/stockfootage/Blow_Hole (Blow Hole, Hawaii Coastline) Blowhole - a cavity located at the end of a sea cave which exits above the cave. When a wave enters the mouth of the cave it will be funneled up towards the blowhole, which can result in quite spectacular blasts of water from the top of the blowhole

24. Erosional Coastline • Sea Cave • Sea Arch • Sea Stack • Sea Cliff • Blowhole • Headland • Wave-Cut Platform • Beach

25. Erosional Coastline • Sea Cave • Sea Arch • Sea Stack • Sea Cliff • Blowhole • Headland • Wave-Cut Platform • Beach

26. Depositional coasts

27. Depositional Coastlines • Created mainly by sediment eroded from another coastline (longshore drift) • Passive margins

28. Features of depositional coastlines Spit - a linear accumulation of sediment that is attached to land at one end, formed by longshore current.

29. Features of depositional coastlines Baymouth Bar (Bay barrier) – formed when a spit extends across the mouth of a bay, closing it off

30. Features of depositional coastlines Lagoon – shallow body of seawater isolated from the ocean. Formed when a bay is completely closed off by a bar

31. Features of depositional coastlines • Barrier islands – narrow, exposed sand bars parallel to but separate from land

33. Features of depositional coastlines • Inlet – narrow passage to the ocean; break in a spit or between barrier islands

34. Features of depositional coastlines Sea island – were once part of the mainland, but rising sea level has cut them off

35. Features of depositional coastlines Tombolo – bridge of sediment connecting a sea island to the mainland

36. Features of depositional coastlines • Delta – coast built out by large amounts of sediment washing off land (usually from a river)

37. Features of Depositional Coastlilnes • Sand Spit • Baymouth Bar • Barrier Island • Tombolo • Beach • Lagoon • Sea Island • Inlet

38. Features of Depositional Coastlilnes • Sand Spit • Baymouth Bar • Barrier Island • Tombolo • Beach • Lagoon • Sea Island • Inlet

39. Beaches

40. Features of depositional coastlines • Beach • Backshore, foreshore, nearshore, offshore • dunes • berm • berm crest • beach scarp • longshore trough • longshore bars

41. Features of a Beach Dunes – ridges of sediment behind the beach which protect land from waves Sand carried/deposited by wind

42. Features of a Beach Berm – an accumulation of sediment that runs parallel to shore and marks the normal limit of sand deposition by wave action Sand carried/deposited by waves

43. Features of a Beach berm crest – the peaked top of the highest berm; usually the highest point on a beach

44. Features of a Beach Beach scarp – a wall in the base of the berm carved by wave action at high tide

45. Features of a Beach longshore trough – underwater trough (depression) parallel to shore caused by wave action and backwash longshore bars – submerged or exposed accumulations of sand below the low-tide line (nearshore)

46. Features of a Beach

47. Features of a Beach • Dunes • Berms • Berm Crest • Longshore Trough • Longshore Bar • Beach Scarp

48. Features of a Beach • Dunes • Berms • Berm Crest • Longshore Trough • Longshore Bar • Beach Scarp

49. Features of a beach

50. Coasts Primary/Secondary