Coastal landscape development Flashcards
(42 cards)
What is a discordant coastline?
A discordant coastline occurs when alternating bands of hard and soft rock run perpendicular to the shoreline.
-This leads to formations of bays and headlands
What is a concordant coastline?
A concordant coastline is when alternating bands of soft and hard rock run parallel to the shoreline
What is an emergent coastline?
An emergent coastline is a stretch of land along the coast that has been exposed to a relative fall in sea level either due to the land rising or the sea falling
- Some land forms found in these are raised beaches, wave cut platforms, sea caves etc
What is a submergent coastline?
A submergent coastline is a coastline that is a result of a rise in relative sea level. This can be due to eustatic change or isostatic change.
-An area where land is now covered by sea
-You can find rias and fjords here
What factors affect how a coast is formed?
-Type of waves approaching the coast
-Direction and strength of prevailing wind
-Types of rock
-Wave refraction
-Erosion of headland
-Deposition in bay
How are bays and headlands formed?
Initially erosion occurs mainly in areas with less resistant rock, forming bays and leaving the more resistant rock sticking out at sea.
Due to refraction the headlands then experience the highest energy waves and are more vulnerable to erosion then in the bays.
-Bays experience low energy waves which allow for deposition and for beaches to form
How is a wave cut notch formed?
When high and steep waves break at the foot of a cliff their energy and erosive action is concentrated into a small area of the rock face.
-The cliff begins to undercut, forming a feature called the wave cut notch
-Further erosion will occur and eventually it will collapse
How is a wave cut platform formed?
The cliff line will begin to retreat after multiple collapses and a gently sloping, relatively smooth wave cut platform is formed at the base of a cliff
How is a stack formed?
As the cliff recedes and the wave cut platform develops the arch will eventually collapse due to gravity. Which leaves an isolated portion of rock as a stack standing above the platform
How is a stump formed?
Overtime the sea will exploit the wave cut notch at the base of a stack leading to its collapse.
-A small portion of the wave cut platform may be left, marking the former position of the stack which is known as a stump
Why does sand form beaches with a more gentle gradient?
Sand tends to form beaches with a more gentle gradient due to its small particle size meaning the sand becomes compact and wet which allows little percolation to occur.
How are ridges and runnels formed?
When there is a gentle gradient on a beach, most of the swash returns as backwash, little energy is lost to friction and material is carried down the beach.
-Ridges and runnels run parallel to the shoreline and are broken by channels that drain the water off the beach.
What causes steeper beach gradients?
The larger the size of the material the steeper the beach as water is able to rapidly percolate through shingle so the backwash is limited in its ability to transport material back down the beach.
What is a storm beach?
A storm beach is a ridge composed of the biggest boulders thrown by the largest waves above the usual high tide mark.
-Created by strong swash at high tide level
What are berms?
Berms are the series of ridges below the storm beach that mark the successively lower high tides as the cycle goes from spring to neap
-They are built up by constructive waves
What are cusps?
Cusps are semi circular shaped depressions which form when waves break directly onto the beach and swash and backwash are strong .
What are the characteristics of swash aligned beaches?
Swash aligned beaches:
-Are generally orientated parallel to incoming wave crests
-Experience minimal longshore drift
-Can be found on irregular coastlines where longshore drift is impeded and waves hit sections of the coast head on
What are the characteristics of drift aligned beaches
Drift aligned beaches:
-Are generally orientated parallel to the direction of dominant longshore drift
-Can have considerable amounts of sediment transported long ways
-initially develop where a section of coastline is fairly regular
-Can extend out from the coastline. E.g. when it meets a estuary
What is a spit?
A spit is an elongated, narrow ridge of land that has one end joined to the mainland and projects out into the sea or across an estuary.
-Usually on a drift aligned coast
What is the difference between simple and compound spits?
Simple spits are either straight or recurved and do not have minor spits or recurved ridges along their landward edge
-Whereas compound spits may have similar features to simple spits but do have recurved ridges and minor spits along their landward side
How are salt marshes formed in coastal areas?
As spits increase in size, there is more sheltered area between the land and the spit.
-Low energy waves enter this area and deposit finer material such as silt and clay.
-These deposits build up and are colonized by vegetation to become salt marshes
What is a tombolo?
A tombolo is a spit that that joins an island to the mainland
What is a bar?
A bar is a is a spit that develops across a bay and connects both sides
-Occurs as there is no strong flow of water from the landward side
What is an offshore bar?
On offshore bar is where a ridge of beach material that remains semi submerged accumulates seaward of the breaker zone
