Costal landscape development Flashcards
Explain how wave-cut platforms are made
Waves break at the foot of a cliff, concentrating erosion along the high-tide line.
This creates a wave-cut notch, overtime this gets bigger and the cliff is undercut until it eventually collapses.
Overtime the cliff retreats.
Explain the costal sequence of caves, arches, stacks and stumps:
Erosion of rock creates fault lines and cracks
Cracks are eroded further (hydraulic action and abrasion) creating a cave
If two caves join up or a single cave is eroded through an arch is formed
Eventually the top of the arch collapses leaving a stack behind which is further eroded to form a stump
Name some landforms of deposition
Beaches Spits Tombolo Offshore bars Barrier beaches Sand dunes
What is a spit and how is it formed?
- Long, narrow form of deposited material
- Longshore drift carries material along the coast but if the coastline changes direction (e.g. because of an estuary) a spit will form.
- The flow of water from the estuary will prevent the spit from extenuating over the mouth.
What is a beach and how is it formed?
- Important temporary store
- Material is deposited when the waves loose energy
Where do salt marshes commonly form and why?
Behind spits as the area is sheltered and contains finer sediment
What is a tombolo and how is it formed?
- A beach that has formed between a small island and the mainland
- Deposition occurs when waves lose their energy, creating a tombolo
What is an offshore bar and how is formed?
- Submerged ridges of sand
- Destructive waves erode sand from the beach and deposit it offshore
- Can act as sediment sinks and stores
What is a barrier beach and how is it formed?
- Where a beach/spit extends across a bay to join two headlands
- Barrier can trap water behind them to form lagoons
What is a barrier island and how is it formed?
- Where a beach becomes separated from the mainland
- Usually made of sand or shingle
What’s required for a sand dune to form?
- large quantities of available sand
- large tidal range
- dominant offshore winds
Describe the progression of sand dunes
Embryo dunes of the first to develop
These grow into larger fore dunes (initially yellow but darken to grey)
Depressions between sand dunes can develop into dune slacks - damper areas
Describe the process of plant succession on sand dunes
First colonising plants are called pioneer species - they have special adaptations to help them survive hostile, salty conditions (e.g. sea rocket, couch grass).
Pioneer plants help bind the dune so it can grow, marram grass is common in fore dunes as it has long roots to seek water.
Different species colonise the dunes until they become stable.
The final community will be adjusted to the climate conditions of the area.
What are saltmarshes?
Areas of flat, silty sediments that accumulate around estuaries or lagoons
Where do salt marshes develop?
- In sheltered areas where deposition occurs
- Where saltwater and freshwater meet
- Where there are no strong tides to wash sediment away
