1. Coastal Processes and Landforms

2. The Coastal Environment
The World Ocean covers 71% of Earth’s surface, and the world’s
shoreline is of enormous length
Earth’s coastlines have tremendous resource, and they are
biologically and geomorphically diverse
Their spectacular scenery bring in more tourists than any other
natural environment, and continue to attract new residents
But they are also subject to any array of natural hazards, and
human-induced environmental problems; ironically, some of
our most polluted waters are found in coastal locations
Global warming and resulting sea level rise will have profound
consequences for coastal zones

4. The Coastal Zone: Definitions
Coastal Zone: General region of interaction between the land and the ocean
Shoreline or Coastline: Constantly changing contact between the ocean surface and the dry land
Sea Level: Average position of the ocean shoreline from which all elevations are measured
Swash: The thin sheet of water rushing towards the shoreline
Backwash: The return flow of water to the ocean
Nearshore Zone: Comprises Breaker Zone, Surf Zone and
Swash Zone (See Fig. 17.1, p. 407 in Text)
Offshore Zone: Undefined zone seaward, beyond the breaker zone

5. Continental Shelf and Continental Slope

7. Waves and Currents
Waves : are travelling, repeating forms of alternating highs and lows called wave crests and wave troughs – induced by Wind
Currents : horizontal movement of ocean water, usually in response to atmospheric circulation  also, rip currents, long shore currents

9. Wave Refraction – waves change directional trend as they approach shore.
Raglan, New Zealand

10. Basic Concepts Repeated sea level changes in the past
Estimated 422 ft. rise since 18,000 years ago
specific landscapes submergent (Passive) or emergent (Active) depending on tectonic change
II. Waves and resultant currents erode, transport, and deposit sediment load.
rocky headlands
beaches
III. Tides affect all coastal life but have little topographic effect.
tidal bore/tidal wave/tsunami

11. Submergent vs. Emergent Coastlines
During the ice ages (or glacial periods) sea level sinks as more water is tied up in glaciers
During interglacial periods sea level rises, flooding many river valleys, creating bays and estuaries
Submergent Coastlines  Rias: drowned river valleys;
Fjords: drowned glacial valleys
Sea levels rise also causes many features of the former shore lie underwater
Also known as Passive-margin Coasts – e.g., Atlantic Coast – because tectonic activity occurs in the middle of the ocean, and the coast is tectonically passive.

12. Submergent Coastlines
Sea level rise inundated many coastal valleys creating bays and estuaries. These coasts are often referred to as Ria coastlines.
Estuary – An arm of the sea that extends inland i.e., an inlet) to meet the mouth of a river.

13. Emergent Coastlines where water level has fallen, or land has risen due to tectonic activity
In areas with “rapid” tectonic uplift, Emergent Coastlines and cliffs are common, and bays are rare
Also called Active- margin Coast – e.g., Pacific Coast
Tectonic forces lift coastlines faster than sea-level rises. Dramatic sea cliffs and marine terraces tower above the sea. Also, sea stacks.
Most activity occurs along active subduction zones and transform plate boundaries.

15. COASTAL PROCESSES AND LANDFORMS
Coastal Erosion – dependent on wave size, angle, and frequency. Focused where waves contact coastline.
Headlands, sea cliffs, bluffs, sea stacks, natural bridges
Beach Erosion
Coastal Transportation – Large waves move beach sand offshore. Small waves push it back onshore.
Wave action creates strong currents parallel to shore – Longshore currents, and longshore drifting.
Also Littoral drifting and beach drifting.
Coastal Deposition – where wave action is reduced, beaches and dunes form.
Beaches, dunes, sand spits

17. Coastal Erosion
Hydraulic action: Sheer physical force, the pounding of waves against coastal rock material.
Abrasion: The process of wearing down or rubbing away by means of friction.

20. Isla Vista Beach, October 2001

21. Isla Vista Beach, December 2002

22. Beach Erosion

24. Formation of
Marine
Terrace

25. Marine Terraces

26. Point Reyes National Seashore California

27. Sea Stacks Port Campbell National Park, Victoria, Australia

28. Natural Bridges and Arches Port Campbell National Park, Victoria, Australia

29. Erosional Landforms
Sea Cliffs: When Waves pound directly against steep land
Sea Caves: Erosion, corrosion and hydraulic action along lines of weakness
Sea Arches: 2 caves meet from each side of hydraulic action of a headland
Sea Stacks: A resistant pillar is left standing – the remnant is called a sea stack
Marine Terraces: Formed by tectonic activity uplift out of reaches of wave action
Headlands: Prortruded land, flanked by receding bays

30. Depositional Landforms
Beach: Landform of coastal deposition, continuous with the mainland  Sandy beaches, Pebble and boulder beaches, White coral reef beaches, Black sandy beaches – in volcanic Big Island, Hawaii
2. Spits: Coastal depositional landforms connected to the mainland at just one end
3. Barrier beaches: long depositional feature constructed parallel to mainland, protection from direct wave attack
4. Lagoon: Body of water partially or fully enclosed by baymouth bar
5. Tombolo: Strip of sediment connecting mainland to an island

32. Tombolo

33. Tombolo

34. Sand Spit

35. Sand Spit

36. Barrier Islands

37. Barrier Islands

38. Point Reyes National Seashore, California

40. Point Reyes Lighthouse

41. Islands Types of Islands
Continental Islands – separated from mainland due to shore submergence
Oceanic Islands – volcanic islands
Atoll – coral formation

42. Tropical Coasts

43. Factors Correlated with Healthy Coral Reef Growth
Water temperature range: 18 – 29C
Normal seawater salinity: 32 – 35 ‰
Clear, transparent water
Little or no sedimentation
Vigorous water motion

50. Tropical Mangroves

51. Mangroves create tidal forests
Mangroves create tidal forests. These rich ecosystems provide habitat for countless creatures and help to stabilize and, by catching sediment, even create coastline.

52. Tides
Low Tide, New Brunswick

53. Tides Tide Cycle
Tides rise and fall with the rising moon, an interval of 24 hours and 50 minutes. There is a bulge on both sides of the earth. Thus two high tides each cycle.
Flood tide (low to high) takes 6:13 and then ebb tide (back to low) is another 6:13.

54. Tides Tide Range
Tide range dependent on relative position of earth, moon, and sun.
Spring Tides - highest tidal range
Neap Tides - lowest tidal range
Occurs every 2 weeks

56. Tidal Patterns in the U.S.

57. Tides
Not significant as a geomorphic agent, but can be very consequential when coinciding with storm surges or tsunamis