Physical Factors - P Flashcards
What are the 5 physical factors affecting coastal landscapes
- winds
- waves
- tides
- geology
- currents
How do we know which factors are most important
It depends on specific location, spatial scale and temporal scales
What does Aeolian mean
- relating to or arising from the action of the wind e.g. erosion, transportation and deposition of sand by wind.
What do Aeolian processes require
require wind energy to operate
What 4 processes can wind affect
- form waves
- erode landforms
- transport and deposition materials
- create and modify landforms
What process is where wind picks up sand
deflation
What is suspension
the transportation of the smallest grains of sand (in the air)
What is saltation
The transportation of medium grains of sand by bouncing along the ground
What is surface creep
the transportation of the largest grains of sand by rolling them across the ground
What is attrition
the breaking down of particles (occurs as sand particles collide during transport
What is the dominant wind
a wind perpendicular to the coast - usually storm winds (90 degrees)
What’s is the prevailing wind
The most common direction of wind in a location
What is an onshore wind
wind blowing from the sea to the land
What is an offshores wind
wind blowing from the land to the sea
What is the source of energy for coastal erosion and sediment transport
wave action
How is wave energy generated
By the frictional drag of winds moving across the ocean surface.
what factors of wind gives the waves more energy
- higher wind speed
- longer fetch
What type of winds drive waves to the coast
onshore winds
What happens when wind blows at an oblique angle (an angle other than 90 degrees)
the resultant waves generate longshore drift
How are waves formed
by the frictional drag of winds moving across the ocean surface
What is wave frequency
the time between waves - usually measured in seconds
which 3 factors combine to generate waves
- strength of wind
- length of time wind blows
- distance over which the wind has been blowing (fetch)
What is the strength of wind measured in
metres per kilometres per hour
what is length of time wind blows measured in
hours
What is the distance over which the wind has been blowing measured in
km (also known as the fetch)
Does a shorter or longer fetch create a more powerful wave
a longer fetch
What is shallow water
water that is the depth of half of a wavelength
What occurs in shallow water
- at this depth the deepest circling molecules make contact with the seafloor: friction slows speed of wave
- wavelength decreases as wave steepens
- top of the wave travels faster and topples over
What is swash
waves moving up the beach
What is backwash
waves moving down the beach
What are some main features of constructive waves
- low in height
- long wavelength
- low frequency (6-8 per minute)
- break by spilling forwards
- strong swash
- weak backwash
Describe how a constructive wave swashes and backwashes
- strong swash which travels a long way up the gently sloping beach.
- backwash returns to sea before r next wave breaks, due to long wavelength, so the next swash is uninterrupted so maintains its energy
In a constructive wave does swash exceed backwash energy
yes
What happens to offshore bars when waves are constructive
the material is moved onshore
As constructive waves have strong swash what happens to beach material
It transports sand up the beach to form a bear,
As constructive waves have a weak backwash what happens to beach material
There is lots of percolation through the sand and little transport of sand down the beach
What are some main features of destructive waves
- greater height
- shorter wavelength
- higher frequency12-14 per minute)
- break by plunging downwards
- weak swash
- strong backwash
Describe how a destructive waves generate swashes and backwashes
- friction from the steep beach slows the swash, so quickly returns as backwash
- the next wave is often slowed by the frictional effect of meeting the backwash of the previous wave
in a destructive wave is the swash energy less than the backwash energy
yes
what happens to longshore bars when there are destructive waves
the eroded material is deposited offshore in longshore bars
what forms when there are destructive waves
a cliff
What happens due to a strong backwash
there is little percolation so more material is moved down the beach
When does wave refraction occur
when a coastline isn’t straight so the process of waves breaking all at the same time is interfered with
What happens to waves in front of headlands
they slow down due to shallower sea - this means the wave is moving at different speeds so wave refraction occurs
Where do waves converge during wave refraction
the headland
Where do waves diverge during wave refraction
the bays
Describe wave refraction
- as waves travel from deep to shallow water, the wavelength shortens, the wave speed slows down, and the wave will refract towards the shallow areas to conserve its energy
What is the energy like where waves converge
the energy is concentrated
what is the energy like where waves diverge
the energy is reduced
How are tides formed
they are formed by gravitational energy
What do tides control
where wave action takes place and where weathering can take place when shorelines are exposed at low tide
What is a tidal range
the difference between the high and low tide - it can influence the development of coastal landscapes
What tidal ranges do enclosed seas have e.g. the Mediterranean
minimal tidal ranges - making wave action and weathering opportunities on exposed shoreline limited and over a very small area
What are the three types of tidal ranges
- Micro tidal - ranges < 2m open ocean coasts (wave dominated)
- Meso tidal - 2-4m (a combination)
- Macro tidal >4m (tide dominated)
What is a spring tide
when the sun and moon align (with earth), the combined effect is to produce a higher than normal tide
What is a neap tide
when the sun and moon are at right angles to each other so lower than normal tides occur
Why are neap tides lower than normal
because the sun and the moon have gravitational pulls in different directions
What produces tidal currents
when the water rises and falls
What is a rising tide called
a flood tide
What is a falling tide called
an ebb tide
What are the two aspects of geology that can influence coastal landscapes
- litholgy - type of rock in that location e.g. resistant rock
- structure - the way the rocks are geologically arranged e.g. joints and bedding planes
Why are Igneous and metamorphic rocks are harder
because of heating and compression during their formation
Where are most igneous and metamorphic rocks found in the UK
North West Britain - forming high cliffs which are more resistant to erosion
Where are the soft rocks found in the UK
on the coastline of Southern and Eastern Britain
What are soft rocks a usually made out of
unconsolidated sands and clays as well as glacial boulder clays and gravels.
Why are soft rocks more easily eroded
they have weaker rocks, with poorly protected bases (3-6m per year)
What can structurally make a rock weaker
Where there is a high concentration of joints and bedding planes
What is a bedding plane
a horizontal boundary between layers of rock
What is a joint
A natural fracture (usually vertical) within the rock
What is strata
Layers of rock
What do more joint and bedding planes means can happen with water
the water can easily pass through as limestone is permeable
The type of rock can determine the landscape that is formed what are the types of rock
- concordant coastline
- disconcordant coastline
What is a concordant coastline
They occur when rock types are parallel to the shore - usually only one rock type
What is a disconcordant coastline
occur when rock types is perpendicular to the shore - usually more rock types
What type of coastline forms headlands and bays
a disconcordant coastline
Why do ocean currents occur
due to the earths rotation
What do ocean currents do
redistribute heat from low latitudes (tropics) to high latitudes (polar regions)
What is an example of an ocean current
the Gulf Stream
The North Atlantic drift
What do ocean currents influence which can influence coastal landscapes
they influence the processes dependant on temperature
What processes do ocean currents influence
Freeze thaw weathering, exfoliation and biological weathering (influenced by temperature)
What type of currents are more localised than global currents
rip currents - influence the movement of sediment on a local scale
how does a rip current work
there is a rip feeder which moves the water past the breaker zone past this point it forms a rip head (similar to a cusp) where fine material can be deposited
What helps to form cusps
a cellular circulation
Where are cusps formed
on beaches in bays
What does erosion between cusps lead to
A deepened seabed which helps to continue the cellular circulation
