Eroded Landforms © Karen Devine 2010
Erosive Processes The sea’s erosive action can be caused by: The sea’s erosive action can be caused by: a) Hydraulic action: the pounding force of the waves. b) Corrosion: when salt water penetrates certain types of rock it can cause them to fracture and break down. c) Corrasion: the abrasive action of water combined with sediments as it washes across rock surfaces. © Karen Devine 2010
The Main Coastal Landforms The main landforms developed by these erosive processes are: The main landforms developed by these erosive processes are: a) headlands b) bays c) cliffs d) rock platforms e) caves f) arches g) stacks h) blowholes. © Karen Devine 2010
Headlands Headlands and bays are formed by the erosion of soft rock by hydraulic action, corrosion and corrasion. Headlands and bays are formed by the erosion of soft rock by hydraulic action, corrosion and corrasion. © Karen Devine 2010
Headlands As the headland is formed it becomes exposed to waves refracting on all sides of it. As the headland is formed it becomes exposed to waves refracting on all sides of it. The waves' erosive processes continue to form caves, arches, stacks and blowholes. The waves' erosive processes continue to form caves, arches, stacks and blowholes. © Karen Devine 2010
Wave-cut Notches When waves apply their force to the base of a cliff they cause a wave-cut notch to form. When waves apply their force to the base of a cliff they cause a wave-cut notch to form. © Karen Devine 2010
Rock Platforms If the impact continues on the wave-cut notch, eventually the cliff is undercut and collapses. If the impact continues on the wave-cut notch, eventually the cliff is undercut and collapses. The remnants become a rock platform. The remnants become a rock platform. © Karen Devine 2010
Caves The corrosive and corrasive forces of waves can continue on the base of a headland causing a cave to form. The corrosive and corrasive forces of waves can continue on the base of a headland causing a cave to form. © Karen Devine 2010
Arches If the wave’s erosive action occurs on both sides of the headland, 2 caves may eventually join. If the wave’s erosive action occurs on both sides of the headland, 2 caves may eventually join. This forms the feature of the coastal arch. This forms the feature of the coastal arch. © Karen Devine 2010
Sea Stacks If waves continue to erode the roof of the cave, then it may eventually collapse leaving a sea stack. If waves continue to erode the roof of the cave, then it may eventually collapse leaving a sea stack. This sea stack is made of very hard rock which has withstood much of the sea’s hydraulic force. This sea stack is made of very hard rock which has withstood much of the sea’s hydraulic force. © Karen Devine 2010
Blowholes Erosion of the weak rocks in the roof of the sea cave can cause a blowhole to form. Erosion of the weak rocks in the roof of the sea cave can cause a blowhole to form. Then, when waves rush in to the cave, the water is forced upwards out of the blowhole and the headland. Then, when waves rush in to the cave, the water is forced upwards out of the blowhole and the headland. © Karen Devine 2010
Pause Time! Play Film of the 12 Apostles. Play Film of the 12 Apostles. Play Film of the 12 Apostles. Play Film of the 12 Apostles. What are the names of the features found at the 12 Apostles site? What are the names of the features found at the 12 Apostles site? Locate the 12 Apostles on a map of Australia. Locate the 12 Apostles on a map of Australia. © Karen Devine 2010