Coastal Erosion
Forces That Shape The
Earth
• The Earth is shaped by both internal and
external processes
• Internally, tectonic processes form the
lithosphere
• Externally gradational processes also shape
the lithosphere
• These include: rivers, winds, glaciers, and
waves
Rivers
• Rivers cut deep valleys and create large
deltas
Winds
• Winds carves beautiful rock formations and
carry sands
Glaciers
• Glaciers flow over continents while slowly
carving out the land and dropping large
boulders…
Waves
• Waves and currents cut into coastlines and polish
sandy beaches….
The Other Gradational Force…
• Humans are a gradational force
• This picture is an example of the effects of over
forestation
Coastal Erosion
• The constant battering of the waves
(14,000 waves per day)
• Effects:
– erode the shoreline
– transport the eroded material
– deposit the eroded material elsewhere
Factors Affecting
Coastal Erosion
• Softer rocks are more easily eroded
• Sea floors that slope gradually have
less erosion because wave break
offshore
• Coastlines oriented perpendicular to
prevailing winds erode more easily
• Rising sea levels increase erosion
rates.
Signs of Coastal Erosion
• Wave-cut notches: An indentation cut into a
sea cliff at water level by wave
• Sea caves: cave formed primarily by the
wave action of the sea
• Sea arches: form where cliffs are subject to
erosion from the sea
• Sea stacks: steep and often vertical column
of rock in the sea near a coast, isolated by
erosion
Wave Cut Notch
Sea Arches, Caves, Stacks
Sea Arches and Sea Stacks
Elephant Rock, PEI
Hopewell Rocks, NB
Preventing Coastal Erosion
• Riprap – a heap of angular boulders
piled along the shoreline
• Breakwater – a wall of boulders built
parallel to the shore to take the brunt of
the breaking waves
Rip Rap
Breakwater