Coasts EQ2 Flashcards
Landforms and Landscapes
How are waves formed?
Friction between wind + water, energy from wind being transferred into water
What 4 factors does wave size depend on?
- Strength of wind
- Wind duration
- Wave depth
- Wave fetch
What way to waves move along?
Circular motion
Becomes elliptical due to friction on seabed
What is fetch?
Uninterrupted distance across water over which a wind blows (distance waves have to grow in size)
What are swell waves?
Wind that caused waves has dropped but remaining waves gradually make their way onshore
How are waves affected by water depth?
Water depth half wave size= friction between wave + seabed slows wave down
Wave length decreases + wave height increase as approach shore
Why do waves break in shallow waters?
Crest of the wave begins to move forward faster than wave trough
What are constructive waves?
Waves with low wave height + long wave length
What are the features of constructive waves?
- Strong swash
- Weak backwash
- Deposited sediment
- On gentle beach profile
What are destructive waves?
Wave height of over 1m + wave length of 20m
What are the features of destructive waves?
- Strong backwash (erodes beach materials + carried offshore)
What is swash?
Flow of water up a beach as a wave breaks
What is backwash?
Water runs back down the beach to meet the next incoming wave
What can be found at high energy coastlines?
e.g. Bristol, SW Wales
- Destructive waves
- Headlands, crack, cave, arch, stack, stump
- Steep cliff
What can be found at low energy coastlines?
e.g. Mediterranean
- Constructive waves
- Sandy beaches
- Sand dunes
- Spits/ bars
- Tombolo
What is beach morphology?
Shape of the beach (width + slope) + features (berms/ ridges)
- Types of sediment found at different locations on beach
What is clastic?
Broken down rock
What is biogenic?
Remains of living organisms
What changes can happen to beach profiles over a long period of time?
- Sediment supply reduced
- Coastal management added
- Climate change
When will most erosion occur?
- Waves are at their highest
- Wave approaches coast at 90° to cliff face
- High tide
- Heavy rainfall
- Debris from previous erosion
What does a summer beach look like?
- Berm in summer
- Constructive waves
- Depositional
- Tidal range dries out sand creating berm (object for dunes)
What does a winter beach look like?
- Sediment removed
- Destructive waves
- Summer accumulation of sediment removed
- Backshore steepness
What features are at the beach?
- Berms + beach scarps
- Storm beach
- Ridges + runnels
- Cusps
What is hydraulic action (wave quarrying)?
- Air trapped in cracks + fissures compressed by force of waves crashing against cliff
- Pressure forces cracks open
- Dislodges blocks of rock from cliff face
What are the influence of lithology in regard to hydraulic action?
- Heavily jointed/ fissured sedimentary
What is abrasion (corrasion)?
- Sediment picked up by breaking waves thrown against cliff face
- Sediment chisels away at surface + wears away
What are the influences of lithology in regard to abrasion?
- Suitably loose sediment has to be available
- Softer sedimentary rocks more vulnerable
What is attrition?
- Acts on already eroded sediment
- Sediment moved around waves + collide between particles chipping off sediment
- Get smaller and rounder
What are the influences of lithology in regard to attrition?
- Softer rock rapidly reduce in size
What is corrosion (solution)?
- Limestone vulnerable by rainwater, seawater
What are the influences of lithology in regard to corrosion?
- Limestone (vulnerable to solution by weak acids)
How is a wave cut platform formed?
- Bottom of cliff eroded by hydraulic action + abrasion
- Notch becomes deeper + overhanging rock becomes unstable + collapse
What is a geo?
Narrow fault guided gullies
What is a blow hole?
Forms when coastal cave turns upwards + breaks through flat cliff top
How are tides formed?
Caused by combined gravitational pull of the moon + sun
What is a neap tide?
Lowest tidal range
- Minimal difference between low/ high tide
- Moon is at right angles to Sun
What is a spring tide?
Highest tidal range
- Alignment of Sun + Moon
What is erosion?
Breakdown of rock due the action of some external force which transports eroded material to new location
