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1. Coastal Landforms: Cliffs & Beaches
2. Coastal Landforms: Cliffs & Beaches By Edward Lin and Lawrence Sit
3. Coastal Landform Environments Influenced by waves, tides, currents, weathering, mass movements, running water, moving ice, and wind.
Almost continuous change; one section wears away as another is built up
E.g.. Cliffs, beaches, deltas, estuaries, salt marshes mangroves, and reefs
4. The Coastal Zone Zone just below low tide level to just above water’s edge at high tide
Many large lakes, inland seas, and oceans have coastal zones
5. Cliffs Steep rock faces
Mainly marine eroded
Storm wave environments - most prominent
Protected coasts - short vertical sections
Humid regions - upper slopes covered with vegetation
6. Where Can They Be Found? Common along convergent plate margins
Also occur along coasts where oceans cut across former mountain ranges
Severed ranges often run at right angles to the coast
7. How Are They Formed? High energy waves erode foot of slope
Abrasion from pebbles flung by waves
A notch is then formed at the cliff base, below the high tide level
As rocks are removed from the notch, upper portion of cliff becomes unstable and rockfalls occur
Processes: weathering mass movements
9. Shore Platforms Horizontal surfaces formed in rock at the base of cliffs
Several types
Wave-cut platforms
Other shore platforms
10. Wave-Cut Platforms Result of cliff erosion
Occur below high tide and slope seaward
As erosion occurs, it is wider and slows the marine erosion of cliffs
Waves enter shallow water across platform which slows momentum
11. Other Shore Platforms Occur on coasts naturally protected from storm waves
Common in tropics, often have horizontal shore platforms
Wetting and drying of rock surfaces between tides makes finely layered rock to break
12. Influence of Rock Type Resistant or recently uplifted rocks – cliffs are higher
Weaker and more resistant rocks alternating and strong rocks that are highly fractured – caves, stacks, and arches form
13. Sea Caves, Stacks, and Arches Sea caves - eroded by waves along lines of weakness at base of cliff and wears away farther than a notch
Stacks - rock pillars isolated from backing cliff by waves removing rocks between them
Arches - stacks still joined at the top to back cliff
- When top portion collapses, stack is left
16. Beaches Coastal depositional landforms composed of loose sand or pebbles
Sand produces wide, flat beaches
Pebbles form narrower, steeper features
Occur in middle and higher latitude
Stormwave environments larger rock fragments from cliffs
17. Tropical Beaches Formed of fine sand brought to coast by rivers
Beach rock - cemented sand with calcium carbonate from dissolved shells
18. Storm Beaches At highest point of beach
Pebbly and steep slope
Pebbles moved by stormwaves
19. Runnels Small flat-floored channels formed by low-tide runoff
Alternate rippled surfaces and low sandy bars formed by breaking waves
More localized than ripples and bars
21. Longshore Drift Longshore currents move sediment parallel to coast
Occurs with steep, storm waves
Sediments pushed up beach at angle of incoming waves
Back wash returns sediment down beach slope
23. Barrier Beaches Elongated sand or pebble banks lying parallel to, but separate from the coastline
Formation factors
Supply of sand moved by longshore drift deposited when carried into deeper water
Dune ridges drowned by rising sea level
Position from longshore drift may combine with sediment brought by currents toward shore
Form offshore bars = semi submerged sand deposits outside breaker zone
24. Lagoons Enclosed and protected by barrier beaches
Fresh water rivers draining into them and develop into wetland marshes
25. Types of Barrier Beaches Bay barriers-connected at both ends to headlands
Bayhead barriers-occur at back of bay
Baymouth barriers-connect headlands with lagoon
Tombolo-bay barrier connecting island the mainland
Barrier islands-not attached to mainland
Barrier spits-attached at one end and extend to open water
27. Vocabulary Coastal Zone-area extending from just above the water’s edge at high tide to just below the low tide level
Shore Platform-coastal landform formed by wave action, weathering, or deposition or calcium carbonate
Wave-cut Platform-shore platform resulting from cliff erosion
Stacks-rock pillars isolated from the backing cliff
Arches-stacks that are still joined at the top with backing cliff
28. Vocabulary Cont. Beach Rock-sand cemented with calcium carbonate
Storm Beach-pebbly and steep slopes at highest point of beach
Runnels-small, flat-floored channels formed by low-tide runoff
Beach Cusps-crescent-shaped sand or pebble accumulations around semicircular depressions
Longshore Drift-process which longshore currents move sediment parallel to the coast
29. Vocabulary Cont. Barrier Beach-elongated sand or pebble banks that are parallel to but separate from the coastline
Offshore bars-semi-submerged sand deposits just outside breaker zone
Lagoons- area of water enclosed by barrier beaches
Bay Barriers-connected at both ends to headlands
Tombolo-bay barrier that connects an island to the mainland
Barrier Spits-attached at one end and extend to open water
Barrier Islands-not attached to mainland
30. Provincial Questions A coastal feature formed by abrasion and undercutting at the base of a cliff is a
A) Beach
B) Headland
C) Recurved spit
D) Wave-cut platform
31. Prov. Questions Cont. Arches, spits, and tombolos are features formed by the action of
A) Ice
B) Wind
C) Rivers
D) Waves
32. Prov. Questions Cont. What is the direction of the longshore drift?
A) southwest to northwest
B) northwest to southwest
C) southeast to northwest
D) northeast to southwest
33. The End