1.b. Coastal landscape systems are influenced by a range of physical factors Flashcards
Physical factors influence coastal landscapes. How
These factors affect how coastal processes work and they operate over different spacial and temporal scales. These factors are often interrelated
How does wind shape the coastline
- wind is the primary source of energy for a range of other processes e.g. erosion and transportation
- aeolian processes e.g. erosion and deposition, contribute to the shaping of coastal landscapes
- onshore winds drive waves towards the coast
- the higher the wind speed and the longer the fetch, the larger the waves and the more energy they possess
How do waves shape the coastline
- waves are undulations on the surface of the sea driven by wind
- waves possess kinectic energy caused by the motion of moving water
- waves also possess potential energy
What is the wave height
This is the difference between the crest and the trough. Wave height is directly proportional to the energy produced
What is the crest
This is the highest point of the wave
What is the trough
This is the lowest part of the wave
What is the wave length
This is the distance between two crests
What is the wave frequency
This is the number of waves per minute
What are swell waves
These are waves that are formed in open oceans and travel over huge distances. They tend to have a long wave length with a wave period of up to 20 seconds
What are storm waves
These are waves with a short wavelength, greater height and wave period of up to 5 econds
What happens when waves enter shallow water
Wave enters shallow water which means friction with the seabed increases. The wave slows as it drags along the bottom. The wavelength drecreases amd successive waves start to bunch up. The wave increases in height andplumges or breaks onto the shoreline
What are spilling waves
Steep waves breaking onto gentle sloping beaches. Water spills gently forward as the wave breaks
What are plunging waves
Steep waves breaking into steep beaches. Water plunges vertically downward as the crest curls over
What are surging waves
Low angle waves breaking onto steep beaches. The wave slides forward and may not actually break
What is the swash
The wash of water up the beach
What is the backwash
The drag back down the beach
What are some properties of constructive waves
- low, long length (up to 100m)
- low frequency (6-8 mins)
- gentle spill onto shore
- the swash loses volume and momentum, leading to a weak backwash
- sediment movement off the beach is low
- swash energy exceeds backwash energy
- material is slowly and gradually moved up the beach
- form berms
What are some properties of destructive waves
- high, steep frequency (10-14 per minute)
- rapid approach to shoreline
- little forward movement of the water
- powerful backwash-sediment is pulled away from the beach
- swash energy is less than backwash energy
- very little material is moved up the beach
- form storm beaches
What is wave refraction
This is the process by which waves break onto an irregularly shaped coastline e.g. a headland separated by two bays
Explain wave refraction
- waves drag in the shallow water approaching a headland
- wave becomes high, steep and short
- the part of the wave in the deeper water moves forward faster
- the wave bends
- the low energy wave spills into the bays as most of the wave enrgy is concentrated on the headland
What are tides
The periodic fall of the sea surface and are produced by the gravitational pull of the moon and the sun
How do tides work
- the moon pulls water towards it, creating a high tide
- there is a compnsating ‘buldge’ on the opposite side of the Earth
- at locations between the two buldges there is a low tide
- as the moon orbits the Earth and the high tides follow it
- the highest tides occur when the moon, earth and sun are aligned so gravitational pull is the stronngest
- resulting in spring tides with a high tidal range
- when the moon and sun are at angles to each other, gravitational pull is weak
- resulting in neap tides with a low range
What is tidal range
This is the vertical difference in height between the consecuative high and low water over a tidal cycle. Tidal range influences where wave action occurs, the weathering processes, and the impact of processes between tides
How does lithology influence coastal landscape systems
- lithology=chemical and physical structure of rocks
- this will impact on physical processes
- weak rocks e.g. clay erode faster than resistant rocks e.g. basalt
- chalk and limestone are susceptible to chemical weathering as their calcium carbonate content is soluble in weak acids
How does structure affect the coastline
- structure refers to features of jointing, faulting and bedding planes in rocks and also their permeability
- permeable rocks include chalk and limestone
- structure affects the shape of the coastline-where rocks lie parallel to the coastline, it tends to be straight or concordant;where rocks lie at right angles to the coast, headlands adnd bays are formed-this is doscordant coastline
- structure affects ‘dip’ of rocks towards the coastline: lanward dipping rock layers lead to steep cliffs and for seaward-dipping tocks layers cliffs follow the angle of the dip
What are currents
These are the permanent or seasonal movement of water in the seas and oceans. There are two types: longhsore and offshore
How do currents affect the coastline
- rip (nearshore) currents transport coastal sediment. They are caused by tidal motion or waves breaking at right angles to the shore. Once rip currents form, they modify the shore profile by creating cusps which help perpetuate the rip current
- ocean (offshore) currents are generated by the Earth’s rotation and the currents are set in motion by the wind. Warm ocean currents transfer heat from low latitudes to high. This transfer affects air temperature and therefore sub-aeolian processes e.g. mass movement
What are the factors that influence coastal landscape systems
- wind
- waves
- tides
- geology e.g. lithology and strructure
- currents
