Geography EQ 1 (Coast) Flashcards
Define coast
A coast is a zone where the land meets and interacts with the sea.
what are the parts on a coast?
- foreshore
- backshore
- offshore
- berm
- cliff
- wave-cut platform
Factors that affect coastal environmental dynamics
- waves
- tides and sea level changes
- currents
- geology
- types of ecosystem
- human activites
define wave
a wave is a rising and falling movement of the water surface that is usually produced by winds blowing across the sea
what does tides affect
processes like coastal erosion, sediment transportation and deposition
define current
a large scale, continuous movement of water in seas
define geology
the arrangement and composition of rocks found in the area
how are waves formed
formed when wind blows over the surface of the ocean . teh friction from the wind causes the water particles near the surface to move in an orbit
crest (parts of a wave)
highest part of a wave
trough (parts of a wave)
lowest part of a wave
wave height (parts of a wave)
verticle distance between the crest and the trough
wavelength (parts of a wave)
the horizontal distance from crest to crest, trough to trough
wave steepness (parts of a wave)
the ration of wave height to wavelength (height/wavelength)
wave period (parts of a wave)
the time waves take to travel through 1 wavelength
wave frequency (parts of a wave)
the no. of wave crests and troughs that pass a fixed point in 1 second
Factors affectig wave energy
- wind speed
- length of fetch
- wind duration
wind speed (Factors affectig wave energy)
greater the wind speed, greater the wave energy
length of fetch + define fetch (Factors affectig wave energy)
fetch - lenth of open water over which the win can blow unobstructed
longer fetch = more energy can be transferred as wind will be able to blow over for a longer period of time
Greater the fetch, the more energy the wave has
wind duration (Factors affectig wave energy)
the longer the wind blows, the more energy waves have
characteristics of waves in the open ocean (Movements of waves)
- long wavelength and low wave height
- water particles move in an orbit
- there is less orbit motion in deeper water
characteristics of waves approaching the store (Movements of waves)
- water gets shallower
- friction between the water particles and sea bed causes base of the wave to slowdown
- wave height will increase
- wavelength will decrease
- wave becomes so steep that the crest topples over
define Swash and Backwash
swash - the water rushing up the slope of the shore
backwash - swash looses energy due to gravity and friction with the land and returns back to the sea as backwash
wat are the 2 types of waves?
constructive wave
destructive wave
characteristics of constructive waves
Points:
gradient
wave height
wave length
frequency
wave period
swash vs backwash
energy of waves
which process is more prominent
- gentle gradient
- low wave height
- long wavelength
- low frequency
- wave period is high
- swash is more powerful than backwash
- low-energy waves
- deposition process more prominent
characteristics of destructive waves
Points:
gradient
wave height
wave length
frequency
wave period
swash vs backwash
energy of waves
which process is more prominent
- steep gradient
- high wave height
- short wavelength
- high frequency
- wave period is low
- backwash more powerful than swash
- high energy waves
- erosion process is more prominent
4 types of erosion
- hydraulic action (agent - waves)
- attrition (agent - rocks)
- abrasion (agent -rocks/sediment)
- solution (agent -soluble materials e.g. sea water)
Define hydraulic action
air in the cracks are compressed by the oncoming waves exerting pressure on the cracks
Define attrition
rock particles break down and become smaller, smoother and rounder as they hit against each other
Define abrasion
as waves break, sediments are hurled against the coast, weakening the cliffs
Define solution
soluble minerals dissolve in the sea water
Define longshore drift
- longshore current flows parallel to the coast and is generated by wind, tides and waves approaching at an angle
- Swash and backwash motion is repeated and causes a zig-zag movement of sediments along the coast
Cliff definition
steep and near- vertical rock surface found along coasts.
How is a wave-cut platform formed?
- Wave erosion is concentrated along a line of
weaknesses, forming a notch. - Prolonged erosion of the notch causes it to
become deeper, forming a cave. - Further erosion of the cave causes the
roof to collapse, and a steep cliff is formed.
4.Further erosion causes the cliff to retreat inland. A
wave cut platform is formed at the foot of the cliff.
What are wave-cut platforms
the cliff will retreat inland and a gentle sloping
platform appears at the base where the cliff used to be. This platform is called a shore platform/
wave-cut platform, which is submerged during high tides.
headlands definition
resistant rocks are less easily eroded by the waves and they remain as headlands,
bays definition
less resistant rocks are more easily eroded and are eroded away to form bays.
why id it that wave erosion along such coastlines cannot carry on indefinitely?
The rate of erosion in the bay will eventually decrease as wave energy decreases with the refraction of the wave front by the
headlands.
Wave Refraction definition
the process by which waves change direction as they approach a coast.
Alittle bit abt wave refraction
Water waves travel faster on the surface of deep water than they do on shallow water
● The change in speed of the wave will cause refraction.
● Refraction = bend or a change of direction
relating wave refraction to coasts
[converge and diverge]
On a coastline with alternating headlands and bays, waves tend to converge on headlands. This gives rise to increased wave height and greater erosive energy.
However, when waves approach bays, they diverge, resulting in decreased wave height and reduced erosive energy.
how are caves arches and stacks related to headlands
Caves, arches and stacks are erosional features commonly found on a headland.
How are headlands and bays fromed?
Waves attack an exposed discordant coast where alternate bands of resistant rocks and less resistant rocks occur at right angles to the coast.
- The coast is eroded unevenly due to the different resistance of the rocks. The more rapid erosion of the less resistant rocks forms the bay. The less rapid erosion of the resistant rock forms the headlands.
formation of caves
- Waves attack a line of weakness to form a notch at the headland. Continued erosion forms a cave.
formation of arches
- An arch is formed when the cave cuts through the headland or meets with
another sea cave on the other side of the headland.
formation of stacks
- Weathering may cause the arch to become unstable and collapse. This leaves behind an isolated pillar of rock called a stack. Continual erosion of the stack reduces the height of the stack, forming a stump.
how are spits formed (simplified)
the accumulation of materials will appear above the surface of water, resulting in a long narrow ridge of sand or pebbles with one end attached to the mainland. This coastal feature is known as a spit.
define beach
a zone of sediment deposition, usually formed from loose sand, gravel, pebbles, broken shells and corals or a mixture of these materials.
how are beaches formed
Wave refraction causes waves to converge at the headlands.
● Erosion is concentrated at the headland.
● Wave refraction causes wave energy to be dissipated at the bay
● Materials eroded at the headlands as well as other materials carried by the waves are deposited at the bay.
● The materials on the beach may be sorted, with the larger materials being deposited inland.
how are spits formed (extended)
- Overtime, the accumulation [1] of materials will appear above the surface of water, resulting in a long narrow ridge of sand or pebbles with one end attached to the mainland. This coastal feature is known
as a spit. [1] - The longshore drift transports material in a zig-zag fashion parallel to the coast [1]. Even when the coastline changes, longshore drift continues to transport material in the original direction
[1]. - Wave refraction or changes in wind direction may cause the free end of the spit to curve to form a hooked spit. [1]
define tombolo
the spit extends seawards and joins an offshore island nearby to form
