COASTAL EROSIONAL LANDFORMS

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COASTAL EROSIONAL LANDFORMS

• GEOL 1053

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LIST OF MAJOR COASTAL EROSIONAL
LANDFORMS(involving consolidated rocks)

• Sea cliffs
• Wave-cut platform
• Sea arches
• Sea stacks
• Sea caves
• Coastal waterfalls

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

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

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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).

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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.

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SEA CAVES

• Deep erosion locally in a sea cliff
• Of weaker rocks
• At tide level
• Blowholes may develop where
  roof collapses

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COASTAL WATERFALLS

• when horizontal cliff erosional retreat is faster
  than stream bed erosion downward
• produces a hanging valley

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