Erosional Landforms Flashcards
Describe the formation of a wave cut platform
Wave energy is focused on the cliffs
Forms a notch which will be exploited until it forms a cave
Above the cliff sub aerial processes are at play which cause the rock and soil to become weaker.
Eventually it cant be supported and falls
Repeated cliff collpases leads to a platform which is further smoothened by abrasion
Explain how wave cut platforms pose a negative feedback loop in the costal system
More erosion = greater length of wave cut platform
Wave cut platform dissipates wave energy
So less erosion occurs
Describe the formation of caves arches and stacks
Fault in cliff is exploited by hydraulic action forming a geo or a cave
Cave is further enlarged by erosional processes
An arch forms when the cave breaks through to other side of headland
Subareial processes take place within the arch that weakens it to point of collapse
Erosion takes place on the stack left to reduce it to a stump
Describe a sandy beach as opposed to a shingle beach
Sandy beaches: Gently slopping - no greater than 5degrees, very little percolation and so most of the water runs off as backwash
Shingle beaches: steeper up to 20 degrees, larger sediment so more percolation hence reduced backwash so reduced erosion
Give four examples of small landforms found on beaches
Ridges and berms - repeated deposition at a high tide mark
Cusps - swash occurs directly onto the beach, where sand meets shingle, curved sides form that channel wster into the centre of the cusp = stronger backwash hence deeper cusp
Ripples - tidal movements
Runnels - breaks in ripples or berms where backwash occurs
Coastlines can be either _____ or _____ aligned , describe both
Swash - waves approach parallel
Drift - waves approach at an angle = longshore drift. Spits etc common here
Compare simple and compound spits
Simple - straight but might have a recurved tip
Compound - have minor spots and recurved tips, caused by wave refraction, esentially forms because a first recurved tip causes another change in direction of the coastline
What is a tombolo?
A spit connecting a mainland area to an island
What is an offshore bar?
An accumulation of sediment carried by costal currents
Where will barrier beaches form? When will this turn into a barrier island
Spit extends across a bay, occurs where there is no offshore current, a salt marsh will form behind it.
Will form a barrier island when sea levels rise
Describe the conditions that allow sand dunes to form
Onshore wind
Large tidal range with a lot of dry sand
Many storm berms
What is a dune slack?
Where water table surfaces inbetween dunes
Where will estuarine landfroms occur?
Describe the succession that occurs to form a saltmarsh
Low costal energy
River water meets saline water so flocculation occurs (clay particles aggregating) At low tide this mud will be exposed.
1) eelgrass grows which slows the currents down
2) halophytes grow and colonise the mudflats, e.g. Cordgrass
3) soil is more bound, which traps more sediment
4) more deposition and decay improves soil
5) complex plants grow e.g. Marsh samphire
6) marsh rises above high tide level= climax community
