Coastal changes and conflict Flashcards
(32 cards)
Describe concordant coasts
- made up the same type of rock
- parallel to the sea
Describe discordant coasts
- rocks type alternates in layers
- perpendicular to the sea
- forms headlands and bays
What are joints ?
small cracks in rock
What are faults ?
larger cracks in rock
Rates of erosion are mainly down to the geology, but what are the other 4 factors ?
(1) geology structure - e.g if soft and hard rocks occur together
(2) ‘wave climate’ - how powerful waves are, wave direction, wave height and how far they travel over open water
(3) local currents and tidal range
(4) groundwater levels - high groundwater is more vulnerable
Describe the formation of headlands
- headlands are left sticking out where hard rock has resisted erosion (erosion of the sock rock forms bays)
- they become more vulnerable to erosion because wave energy is concentrated there
Describe the formation of bays
- bays form due to rapid erosion of soft rock / less resistant rock
- they then become sheltered by headlands and stop eroding
How are caves formed ?
when the waves erode a weakness in the rock e.g a joint or a fault
How are arches formed ?
when two caves erode back from either side of a headland and meet in the middle
How are stacks formed ?
when an arch collapses
How are stumps formed ?
when a stack is eroded by wind and water
What are wave cut platforms and how are they formed ?
- areas of flat rock at the base of the cliff
1. rock face overhangs
2. wave-cut notch is undercut by the waves
3. cliff retreats inland and overhanging rock collapses
4. wave-cut platform is formed
What are the 4 process that erode the coast ?
- hydraulic action
- abrasion
- attrition
- solution
Describe how hydraulic action erodes the coast
- the sheer weight and impact of water against the coastline, will erode the coast
- waves compress air in cracks in rock, forcing them apart and weakening the rock
Describe how abrasion erodes the coast
breaking waves throw sand and pebbles against the coast during storms
Describe how attrition erodes the coast
the rocks and pebbles carried by the waves rub together and break down into the smaller pieces
Describe how solution erodes the coast
chemical action on some rocks, especially limestone
What are the sub-aerial processes that also contribute to coastal erosion ?
MECHANICAL WEATHERING :
- freeze thaw, water in cracks freezes and expands, over time the crack widens and pieces of rock fall off
CHEMICAL WEATHERING :
- occurs when the rock’s mineral composition is changed
BIOLOGICAL WEATHERING :
- caused by plants and animals e.g. tree roots widen gaps in rocks
MASS MOVEMENT :
- the downhill movement of material under the influence of gravity, the different types depend on…
- the material involved
- the amount of water in the material
- the nature of the movement
When do slumps occur ?
when the rock (often clay) is saturated with water and slides down a curved slip plane
When does sliding occur ?
when loosened rocks and soil tumble down the slope
Describe the stages of long shore drift
- waves approach the coast at an angle
- swash pushes sand and gravel up the beach at the same angle
- backwash carries sand and gravel back down the beach at 90oC to the coastline
- sand and gravel move along the beach in a zigzag fashion
- sand is lighter than gravel so moves further up the beach
What are the 4 types of transportation ?
TRACTION :
- large boulders are rolled along by the waves
SALTATION :
- smaller stones are bounced along the sea bed
SUSPENSION :
- sand and small particles are carried along in the flow
SOLUTION :
- some minerals are dissolved in seawater and carried along in the flow
Describe the process of deposition
the load carried by waves is deposited by constructive waves, different factors effect deposition…
- sheltered spots
- calm conditions
- gentle gradient offshore causing friction
all reduce the wave’s energy
What are the 3 landscapes formed from deposition ?
- beaches
- spits
- bars
