Slides on Coastal erosion, deposition and transport for Leaving Certificate Geography (Irish education system)

2. A watery Planet…

3. Waves
Waves are one of the most powerful processes shaping our
coast
The power of waves is influenced by the strength of wind and
by the fetch, the length of water the wave travels over before
hitting land
The fetch on the west coast of Ireland is obviously a lot bigger
than the fetch on the east coast
Bigger fetch = more powerful waves = more eroded coastline
One glance at the Irish coast tells us which coast suffers more
from erosion
http://www.marine.ie/home/publicationsdata/data/buoys/

4. Ireland from space

5. Swash and Backwash – p 158
Swash – the rush of water up a beach after a wave breaks
(powerful)
Backwash – the returning water to the sea (less powerful)
Constructive Waves – Break gently, far from shore and swash
pushes material into shore, very weak backwash
Destructive Waves – Break very close to shore, very powerful
backwash

6. Processes of Erosion
Hydraulic action – power of water (waves)
Abrasion – Rocks/sand thrown against the coast
Compressed Air – trapped in small crevices in the rock
by waves, this causes mini “explosions” which
eventually shatter the rock
Attrition – Rocks wearing off each other
Solution – Salts in seawater dissolving rock (esp
sedimentary rock)
Wave refraction – waves bending on contact with the
coast, concentrating it’s effects in certain areas

7. Processes of Deposition &
transport
This requires three basic conditions
Gently sloping beaches to reduce wave energy
Shelter from strong winds/currents (e.g. in a Bay)
Constructive waves
For Transport, the main process is Longshore Drift, also
known as Littoral drift

8. Longshore drift

9. Landforms of Erosion
Cliffs and Wave Cut Platforms (Cliffs of Moher)
Bays and Headlands (Dublin Bay, Bray Head)
Sea Caves(Cliffs of Moher)
Sea Arches (Old Head of Kinsale)
Sea Stacks (Dun Briste, Co. Mayo)
Sea Stumps (Cliffs of Moher)

10. Cliffs and Wave Cut Platforms

11. Cliffs of Moher

12. Cliffs of Moher

13. Cliffs and Wave Cut Platforms –
P161

14. Bays and Headlands – p 163

15. Bays and Headlands
Hard Rock – Erodes Slowly
Soft Rock – Quickly Eroded

16. Sea Cave – p164

17. Cliffs of Moher
Sea Cave
Sea Stump

18. Sea Arch – p164

19. Sea Stack – Dun Briste, Co. Mayo

20. Blow Hole

21. Coastal Deposition
Whatever gets eroded from one area on the coast eventually
gets deposited in another area – nature always balances the
books
The rate of erosion also affects the rate of deposition – an area
with mostly hard rock (e.g. Granite) will erode slowly and thus
have little material for deposition
Coastal deposition features (e.g. beaches) often have
important economic benefits such as tourism

22. Beaches
Beaches are not only formed from sand – mud, shingle and
stones can also form beaches – however these beaches are
unattractive for tourism
For a beach to form you need
A sheltered area to trap sediment
Longshore drift to transport material to the beach
Constructive waves to deposit beach material between the high
and low tide marks

23. Storm Beach

24. Storm Beach

25. Storm Beach
Backwash is too weak to drag stones
back

26. Beach berm
Berms

27. Cusps

28. Ripple Marks