1. Coastal Processes and Terrain
Chapter 20
Coastal Processes and Terrain

2. Coastal Processes and Terrain
Forces That Shape Coastlines
Coastal Sediment Transport
Coastal Deposition
Coastal Landforms
Depositional Landforms
Shorelines of Submergence
Coral Coasts

3. What are coastlines? Coastlines are the transition from land to water
Not permanent features
Always subject to erosion & deposition
They are at the interface of the 3 major components of Earth’s environment:
Hydrosphere
Lithosphere
Atmosphere

4. Coastal Processes
Wind is a major force – it moves the water, creating waves and currents
Waves & currents shape coastlines and create topographic features
Waves = erosion = headlands
Currents = deposition = beaches & sandbars

5. Coastal Processes Tides Diastrophic Events Sea or lake level change
Earthquakes
Volcanoes
Sea or lake level change
Tectonic forces
Eustatic change

6. Exceptions to Lakeshore Change
Tidal range is insignificant
Water level rise/fall different process
Coral reefs occur only in tropical or sub-tropical oceans.
Force of ocean water creates more dramatic topographic features

7. Waves Waves are agents of erosion
Headlands are promontories of sloping land projected into the sea

8. Waves Appear to move but don’t, except when they break
Energy passes through the water, causing the water to undulate
Most are wind generated – action of friction of wind moving across water
Transfer of energy from wind to water initiates wave action
Small number of waves from volcanic or diastrophic activity

9. Development of Waves

10. Wave Refraction

11. Eustatic Sea Level Change
Sea level change due to amount of water in sea/ocean
Related to action of continental ice sheets
Ellesmere Island, Canada

12. Tides
Cavendish Beach, PEI
Bay of Fundy, NS

13. Tidal Characteristics
Not significant agents of erosion
Significant erosion only in narrow bays, margins of shallow seas, and passages between islands

14. Normal High Tides What you should know about tides:
The Moon pulls at Earth – the Sun pulls at Earth and this is what causes tides
Position of Sun, Moon & Earth cause variation in tides

15. Highest Tidal Ranges

16. Stream Outflow
Madagascar
Stream outflow is a major contributor of sediment to oceans
This sediment is then transported by coastal waters

17. Erosion – Rocky Coastline
Most erosion along the coast is due to wave action
Air is forced into cracks in the rocks as the wave hits the shore
When the wave recedes, the air expands loosening the sections of rock
This is a major process of erosion
Port Campbell, Australia

18. Erosion – Cliff Coastline
Wave Cut Notch
b) Erosion at sea level or just above
c) As notch is cut, cliff is undercut and falls away
d) The cliff face retreats, until it reaches bedrock - then you have a headland

19. Formation of Arches 1985 1992 Victoria, Australia
Continuous pounding wave action
1992

20. Erosion - Sand Currents and tides cause erosion
Storms accelerate erosion
A major storm can remove an entire beach in a few hours – eroding down to the bedrock

21. Sediment Transport
Nearly all sediment transport on coastlines is accomplished by wave action and local currents
Mechanisms:
Longshore Currents strike at an angle almost parallel to the shore - “along the shore”
Beach Drifting is downwind displacement of particles along coast
Movement with ebb and surge of tide tumbles particles and reduces size

22. Coastal Sediment Transport
Longshore Current

23. Deposition Most coastal deposition is of fine sand particles
During storms larger particles/pieces can be moved and deposited
Sediment Budget is the balance of eroded and deposited material

24. Coastal Landforms Depositional Landforms Shorelines of Submergence
Beaches
Barrier Islands/Lagoons
Spits
Shorelines of Submergence
Fjorded Coasts
Wave-Cut Cliffs and Platforms
Marine Terraces
Coral Coasts

25. Beaches
An exposed deposit of loose sediment adjacent to a body of water
Backshore: landward of HWL
Foreshore: zone of tidal rise & fall
Offshore: zone always underwater

26. Barrier Islands
Long narrow sandbars built up in shallow offshore water
Usually parallel to shore

27. Barrier Islands and Lagoons
Water is isolated between barrier islands and main land
Eventually merge with barrier and mainland if sediment deposit not interrupted

28. Spits
Linear deposit attached to land at one end and extending into open water in down current direction

29. Coral Coasts
In tropical oceans, most continents and islands are fringed with coral reefs
The coral is composed of polyps – tiny marine animals
They secrete external skeletons of calcium carbonate
Great Barrier Reef, Australia

30. Attached to the coast of volcano
Fringing Reefs
Attached to the coast of volcano

31. Barrier Reefs and Atolls
Barrier reef is aging fringe reef
Volcano is sinking and lagoon forms between reef and volcano
Atoll is a ring shaped coral structure surroundig a landless lagoon
Usually just at sea level

32. Coral Reefs of the World