EQ2 Coasts Flashcards
(77 cards)
What are waves caused by
The action of wind dragging on the surface of the sea creating friction
Energy transferred from wind to water
What factors does the formation of a wave depend on
Wind velocity
Fetch - distance over which wind blew
Duration - period of time of wind blowing
What are waves characterised by ?
Wave height ( trough to crest)
Wavelength (crest to crest)
Period (time interval between arrival of consecutive crests)
Wave propagation direction
What are swell waves and how do they form
Waves generated by energy beneath the oceans surface - don’t need local wind
Originate in mid ocean
Maintain their energy for thousands of miles
Build up over time so Greater fetch = larger wave
How are tides formed
Formed by gravitational pull of the moon acting on water in earths surface
Cause high tides to happen What are some examples of processes which occur in a high energy coastline twice a day with 12 hour intervals
What is beach morphology
The shape of a beach including width and slope
Includes features such as berms, ridges and runnels, as well as type of sediment
How do beaches vary seasonally
Winter beach :
Berms and some dune eroded
High water
Offshore Bars formed
Summer beach :
Dunes and berms deposited
What are storm beaches
Furthest point of beach from tideline
Happen after severe storms and involve high energy deposition of very coarse sediment
What are berms
Made from shingle or gravel
Formed as a result of summer swell wave deposition
What is abrasion
When waves advance they pick up sand and pebbles from the sea bed
When waves break at base of cliff, transported material is hurled at cliff foot, chipping away at rock
What is hydraulic action
When a wave advances, air is trapped and compressed in joints or between the wave and the cliff
Wave retreats and cliff expands
Process weakens joints and cracks and causes rock to break off
What is corrosion/ solution
Cliffs are formed from alkaline rock, weak acid solution in sea can dissolve them
What is attrition
The gradual wearing down of rock particles by impact and abrasion
Gradually reduces particle size and makes stones rounder and smoother
Ultimately becomes sand
What is erosion rate influenced by
Wave type
Season
Geology and rock type
Lithology
Type of coastline (C or D)
What is a sediment cell
An area of a coast often hemmed by physical barriers
Contains a sediment budget in dynamic equilibrium
Fed by sources of sediment and contains sinks and stores
What are some examples of mechanical weathering
Freeze thaw
Salt crystallisation
What are some examples of chemical weathering
Carbonation
Hydrolysis
Oxidation
What are some examples of biological weathering
Plant roots
Rock boring
how are caves created
cracks at base of headland widened by erosional processes, and weathering such as salt crystallisation and wet and dry weathering
wave cut notches form, are eroded back to form caves
how do caves deepen?
wave refraction distorts wave direction
destructive waves concentrate energy on sides of cave
how are arches formed
wave refraction effects all 3 sides of headland. If 2 caves are aligned, waves can cut through to form arch
base of arch widened by wave cut notches
how do blowholes form
vertical joints exposed by tall destructive waves
joints weathered from above by carbonation in limestone
how do stacks form
arch becomes unstable and collapses under own weight to form pillar of rock
how is stump formed
stack eroded at base, forming wave cut notches
sub aerial processes weaken from above
exposed stack will collapse