Formations Flashcards
(6 cards)
Formation of a stack
-Headlands with weaknesses such as joints, faults of cracks are eroded by the sea to form caves, e.g Till Whim cave.
-Erosion takes place due to hydraulic action, where pounding waves compress trapped air in the rocks, creating an explosive blast that weakens and loosens the rocks fragments.
- Corrasion occurs, when rock fragments are thrown against the headland,wearing away the rock.
-Over time, erosion on both sides of the headland cuts through the backwall and enlarges the cave to create an arch, e.g Durdle door.
-Continued erosion at the end foot of the headland and the effects of vibrations on the roof of the arch knocks down the roof of the arch, leaving a stack insolated from the headland. E.g old harry
Hydraulic cycle within drainage basin
Transfer: water may move over the surface or the land as overland/surface flow, flow into the soil in a process called infiltration. Water can move downhill through the rocks as groundwater flowzz
Formation of cliffs and wave cut platform
-Weaknesses such as joints, faults or cracks in cliffs are undercut by erosion to form a wave-cut notch
-Corrasion occurs when rock fragments thrown against the headland breaking down the cliff face, wearing away the rock (2 marks).
• Corrosion occurs when carbonic acid in sea water weather limestone and chalk (2 marks)
-The rock above overhangs over the notch and, as erosion continues, the notch enlarges until the unsupported overhang collapses due to the weight (1 mark)
• The new cliff face is then eroded and through time, the cliff retreats inland, leaving a gently-sloping rocky surface called a wave-cut platform (1 mark).
• The platform is abraded by rock materials, with rock pools and pot holes forming, evident at low tide (1 mark).
Longshore drift (must be explained before sand bar,sand spit, tombolo)
Sand spits, bars and tombolos are formed by the process of longshore drift (1 mark).
• Swash is where waves, driven by prevailing wind push material up the beach at an angle (1 mark)
• The returning backwash is dragged back by gravity down the beach at right angles. (1 mark)
• Material is carried by the water along the coastline in a zig-zag pattern and will eventually be deposited on when the waves lose energy (1 mark).
Formation of sand spit
Sand spits, bars and tombolos are formed by the process of longshore drift (1 mark).
• Swash is where waves, driven by prevailing wind push material up the beach at an angle (1 mark)
• The returning backwash is dragged back by gravity down the beach at right angles. (1 mark)
• Material is carried by the water along the coastline in a zig-zag pattern and will eventually be deposited on when the waves lose energy (1 mark).
Spits form when there is a change in direction on a coastline (1 mark), allowing a sheltered area for deposition (1 mark).
• Material slowly builds up to appear above the water (1 mark).
• The spit develops as long as the supply of deposits is greater than the amount of erosion (1 mark).
• The shape can become hooked or curved at the end in response to changes in wind direction/currents (1 mark).
• A salt marsh may form in a sheltered area behind a sand spit (1 mark).
• An example is Spurn Head. (1 Ex mark)
Sand bar formation (must explain longshore drift AND sand spit before)
