Title: COASTAL EROSIONAL LANDFORMS
1COASTAL EROSIONAL LANDFORMS
2LIST OF MAJOR COASTAL EROSIONAL
LANDFORMS(involving consolidated rocks)
- Sea cliffs
- Wave-cut platform
- Sea arches
- Sea stacks
- Sea caves
- Coastal waterfalls
3WAVE-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
4Wave-cut platform Headland and beach cut on
Oligocene Amuri Limestone. (south of Kaikoura,
South Island, New Zealand)
Wave-cut platform
5SEA ARCHES
- Differential weathering at tide level along a
narrow promontory. - Natural bridge (sea arch) in Plio/Pleistocene
limestone (North coast of Aruba).
6SEA 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).
7SEA 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.
8SEA CAVES
- Deep erosion locally in a sea cliff
- Of weaker rocks
- At tide level
- Blowholes may develop where
roof collapses
9COASTAL WATERFALLS
- when horizontal cliff erosional retreat is faster
than stream bed erosion downward - produces a hanging valley
10Evolution 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.
11Large 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
12Rocky, tectonically active, immature coastline
with numerous small offshore sea stacks and
islands(San Francisco-Mendocino area, California).