Landform Formations Flashcards
(33 cards)
How are headland and Bays formed
On a discordant coast
Less resistant rock gets eroded, forming bays while more resistant rock forms headlands. Headlands receive high-energy waves, so are more vulnerable to erosion. Bays experience low energy waves, allowing sediment to build up forming beaches
Where are headlands and bays found
Swanage bay
San Fransisco bay
Flamborough head
What are the processes and outputs of headlands and bays
Processes:
Differential rates of erosion of the Different rocks
Wave refraction
Erosion of the headland
Deposition in the bays
Outputs:
Headland and Bay
Erosion of the Headland
Deposition in the bay
How are wave cut platforms formed
The base of a cliff is eroded until it’s undercut, forming a wave cut notch. Further erosion increases the stress on the cliffs until they collapse. As the cliff retreats, a wave cut platform is formed at the base of the cliff. As the platform continues to grow, the waves break further out to sea, so energy is dissipated, reducing the rate of erosion
Examples of wavecut platforms
Flamborough head
How are caves, arches, stacks, and stumps formed
Cracks are eroded by the sea, forming a cave. The cave is eroded all the way through making an arch. The arch will eventually collapse due to gravity and sub-aerial processes leaving a stump
Examples of cave, arch, stack, stump
Old Harry’s rock
Twelve apostles
How are geos formed
Weak points are eroded more rapidly by wave action than the resistant rocks around them. Horizontal collapse
How are blowholes formed
From mine shafts collapsing in on themselves
Weakening the cliff face, causing caves, which then, as the caves deepen and widen, they create a blowhole when the roof collapses
Verticle collapse
Examples of blowholes and geos
Geo-Huntsman’s leap
Blowhole from a mine-Trevone
Blowhole-lulworth cove, swanage
How are beaches formed
Normally, sand or shingle
Material builds up from a strong swash and a weak backwash. Sand tends to produce beaches with more gentle gradients as its small particle size means the sand becomes compact when wet, allowing little percolaton
How are spits made
Material carried by LSD. When a coastline changes direction, sand and shingle build up in a sheltered area. When the water loses its ability to transport material further, it is deposited. A curve forms from wave refraction.
Examples of spits
Spurn point
Sandy hook
How are tombolos formed
A spit that joins an island to a mainland. Deposition occurs when waves lose energy building up a tombolo. Can be covered at high tide
Examples of tombolos
Chesil beach
St Ninians-Shetlands
How are bars formed
A spit forms across a bay where there is no strong flow of water. A lagoon is formed behind.
How are offshore bars formed
Created by waves offshore from the coast. Destructive waves erode sand from the beach with their strong backwash and deposit it offshore. Act as sediment sinks as well as they absorb wave energy, reducing the impact on the coastline
How are barrier breaches formed
A beach or spit extends across a bay to join 2 headlands. Elongated bank of deposited sand or shingle parallel to the coastline and not submerged but incoming tides. Can trap water behind creating a lagoon
How is a barrier island formed
Beach becomes separated from the mainland. Common in areas with low tidal ranges and where offshore coastline is gently sloping
How are dunes formed
Accumulations of sand shaped by the wind resulting in a positive feedback system
Inputs for sand dune
Strong onshore winds
Large tidal range
Obstacle to trap the sand
Vegetation growth
Sand mostly moved inland by saltation
Differential heating means localised differences in atmospheric pressure, which means during the day the wind on the coastal fringe is generally from the sea.
Large tidal range means large amounts of sand are exposed at low tide
What order are the dunes in
(Every Football fan Yells Grumpy David Moyes)
Embryo
Fore
Yellow
Grey
Dune slack
Mature
How are mudflats and salt marches formed
River sediment is deposited in water close to the edges of the river away from the faster tidal currents. Rising tides create a buffer to rivervflow. Most of the accumulated sediment is mud, which develops into saltmatches. Flocculation means heavy particles sink to the bed. At low tide, the inter-tidal area of mud if left exposed. Overtime mudflats develop into salt marches
How are deltas formed
Sediment deposited by rivers and tidal currents at a faster rate than waves and tides can remove it.
