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COASTAL EROSIONAL LANDFORMS

COASTAL EROSIONAL LANDFORMS. GEOL 1053. LIST OF MAJOR COASTAL EROSIONAL LANDFORMS (involving consolidated rocks). Sea cliffs Wave-cut platform Sea arches Sea stacks Sea caves Coastal waterfalls. WAVE-CUT PLATFORMS.

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COASTAL EROSIONAL LANDFORMS

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  1. COASTAL EROSIONAL LANDFORMS GEOL 1053

  2. LIST OF MAJOR COASTAL EROSIONAL LANDFORMS(involving consolidated rocks) • Sea cliffs • Wave-cut platform • Sea arches • Sea stacks • Sea caves • Coastal waterfalls

  3. WAVE-CUT PLATFORMS • Erosion of a sea cliff leaves a gently sloping rock platform that is visible at low tide. It may be partly covered by a veneer of coarse-grained sediments, even cobbles and boulders. wave-cut notch wave-cut platform

  4. Wave-cut platform: Headland and beach cut on Oligocene Amuri Limestone. (south of Kaikoura, South Island, New Zealand) Wave-cut platform

  5. SEA ARCHES: • Differential weathering at tide level along a narrow promontory. • Natural bridge (sea arch) in Plio/Pleistocene limestone (North coast of Aruba).

  6. SEA STACKS • More resistant rock remains as a promontory because of compositional or structural differences which lead to differential weathering & collapse of arches. • Sea stacks and sea arches in cyclically bedded Upper Cretaceous chalks (French Channel coast).

  7. SEA STACKS(CONT.) Sea stacks along a cliffed, rocky coastline (Victoria coast, Australia). Large waves from the Southern Ocean have eroded fractured sandstones into a series of headlands and isolated stacks (remnants of headlands). Although clearly vulnerable to wave erosion, such stacks survive for tens to hundreds of years.

  8. SEA CAVES • Deep erosion locally in a sea cliff • Of weaker rocks • At tide level • “Blowholes” may develop where roof collapses

  9. COASTAL WATERFALLS • when horizontal cliff erosional retreat is faster than stream bed erosion downward • produces a “hanging valley”

  10. Evolution of a drowned coastline (ria coast): - erosion occurs - sediments form - shoals develop - depositional landforms (beaches, spits, etc.) develop There is a tendency for the coast to straighten - all other factors being equal (more resistant rocks will form headlands while the less resistant rocks will form embayments). Bays fill with sediments.

  11. Large erosional talus blocks of Pleistocene limestone that have tumbled down the erosional escarpment that exposes the Scotland Fm. in the background. Note the wave-cut notches at the base of the talus blocks. Such notches, cut by physical and biological processes, are excellent indicators of sea level and can be preserved in some circumstances. Human bathers. (Bathsheba, Barbados) END OF FILE

  12. Rocky, tectonically active, immature coastline with numerous small offshore sea stacks and islands(San Francisco-Mendocino area, California).

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