Coastal Landforms: Cliffs Beaches

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