Eroded Eroded LandformLandform

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© Karen Devine 2010

Erosive ProcessesErosive Processes The sea’s erosive action can be The sea’s erosive action can be

caused by:caused by:a)a) Hydraulic actionHydraulic action: the pounding : the pounding

force of the waves.force of the waves.b)b) CorrosionCorrosion: when salt water : when salt water

penetrates certain types of rock it penetrates certain types of rock it can cause them to fracture and can cause them to fracture and break down.break down.

c)c) CorrasionCorrasion: the abrasive action of : the abrasive action of water combined with sediments water combined with sediments as it washes across rock surfaces.as it washes across rock surfaces.

© Karen Devine 2010

The Main Coastal LandformsThe Main Coastal Landforms

The main landforms The main landforms developed by these developed by these erosive processes are:erosive processes are:

a)a) headlandsheadlandsb)b) baysbaysc)c) cliffscliffsd)d) rock platformsrock platformse)e) cavescavesf)f) archesarchesg)g) stacksstacksh)h) blowholes.blowholes.

© Karen Devine 2010

HeadlandsHeadlands

HeadlandsHeadlands and and bays are formed bays are formed by the erosion of by the erosion of soft rock by soft rock by hydraulic action, hydraulic action, corrosion and corrosion and corrasion.corrasion.

© Karen Devine 2010

HeadlandsHeadlands As the headland is formed it becomes exposed to As the headland is formed it becomes exposed to

waves waves refractingrefracting on all sides of it. on all sides of it. The waves' erosive processes continue to form The waves' erosive processes continue to form

caves, arches, stacks and blowholes.caves, arches, stacks and blowholes.

© Karen Devine 2010

Wave-cut NotchesWave-cut Notches

When waves When waves apply their apply their force to the force to the base of a cliff base of a cliff they cause a they cause a wave-cut wave-cut notchnotch to to form. form.

© Karen Devine 2010

Rock Platforms Rock Platforms

If the impact If the impact continues on the continues on the wave-cut notch, wave-cut notch, eventually the eventually the cliff is undercut cliff is undercut and collapses. and collapses.

The remnants The remnants become a become a rock rock platform.platform.

© Karen Devine 2010

CavesCaves

The corrosive and The corrosive and corrasive forces of corrasive forces of waves can waves can continue on the continue on the base of a base of a headland causing headland causing a a cavecave to form. to form.

© Karen Devine 2010

ArchesArches

If the wave’s If the wave’s erosive action erosive action occurs on both occurs on both sides of the sides of the headland, 2 caves headland, 2 caves may eventually may eventually join. join.

This forms the This forms the feature of the feature of the coastal archcoastal arch..

© Karen Devine 2010

Sea StacksSea Stacks If waves continue to erode the roof of the If waves continue to erode the roof of the

cave, then it may eventually collapse leaving a cave, then it may eventually collapse leaving a sea stacksea stack. .

This sea stack is made of very hard rock which This sea stack is made of very hard rock which has withstood much of the sea’s hydraulic has withstood much of the sea’s hydraulic force.force.

© Karen Devine 2010

BlowholesBlowholes

Erosion of the weak Erosion of the weak rocks in the roof of the rocks in the roof of the sea cave can cause a sea cave can cause a blowhole to form. blowhole to form.

Then, when waves Then, when waves rush in to the cave, rush in to the cave, the water is forced the water is forced upwards out of the upwards out of the blowhole and the blowhole and the headland.headland.

© Karen Devine 2010

Pause Time!Pause Time!

Play Film of the 12 Play Film of the 12 Apostles.Apostles.

What are the What are the names of the names of the features found at features found at the 12 Apostles the 12 Apostles site?site?

Locate the 12 Locate the 12 Apostles on a map Apostles on a map of Australia.of Australia.

© Karen Devine 2010