EQ2 Flashcards
explain how different wave types result in different beach profiles (6)
the main types of waves are those of constructive and destructive, each of which have different characterstics and that can be seen to occur in different environments and seasons, resulting in contrasting beach profiles.
Constructive waves occur in lower energy environment mainly during summer months, resulting in a summer beach profile. Waves have a stronger swash than backwash resulting in a steeper beach gradient at the back of the beach as waves are less frequent dissipating energy over a wider area. The strong swash then carries larger pieces of sediment and deposits at the top of the beach creating berms. Due to waves being less frequent and wave energy being absorbed by the wider beach they therefore have a weak backwash meaning as a result beach material drains back to the sea via percolation and the beach is smaller at the shoreline.
Destructive waves are more common in winter conditions where waves are more powerful and of higher energy and frequency, resulting in a winter beach profile. This involves waves having a much stronger backwash than swash, eroding the coast and berms with the backshore carrying sediment off the shore and depositing this at offshore bars and creating beach loss rather than beach gains. This results in a smaller beach gradient compared to a summer beach profile, with this backswash then also exerting a rip as it drags sediment away from the beach, further beach loss.
explain two processes of erosion that increase the importance during storms (6)
Hydraulic action increases in importance during storms that associated with strong prevailing winds that means destructive waves (with a high frequency (15 or more per minute) and short wavelength (up to 20m)), especially, exploit lithological weaknesses in coastal geology, including fissures and joints, with greater force as waves have more kinetic energy and are more frequent. Attrition increases in importance as lots of sediment is eroded from cracks, fissures and joints - especially in clastic, permeable sedimentary rocks that are saturated with a high pore water pressure, contributing to mass movement that dislocates sediment - meaning that there is more sediment (and with more energy in high-energy stormy conditions) to collide with each other, contributing to pebbles becoming more rounded and smaller quickly.
explain the characteristics of a drift-aligned beach (6)
A drift-aligned beach refers to a beach in which wave crests approach at angle to the coast (e.g. 30°) meaning that there is consistent longshore drift (the lateral movement of sediment in a zig-zag pattern, determined by prevailing winds) meaning that beaches remain narrow as there is a constant removal of sediment - along with an absence of berms. Elongated depositional landforms can form, including spits (e.g. Spurn Head, Holderness Coast) and bars (e.g. Chesil Beach, Dorset).
assess the significance of different weathering and mass movement processes in coastal landscapes systems (12)
weathering is the gradual breakdown of rock and situ. There are 3 types of weathering which are mechanical,chemical
and biological weathering. Mass movement is the movement of weathered material downslope as result of gravity. There are four types of mass movement which are rockfall, rotational slumping, transitional slides, topples and flows.
weathering is described as the breakdown of rock with this being broken down into 3 main types, each ocuuring often within different climatic conditions and alternating drift and coastal system but each playing a large role within creating sediment for further erosion to occur. For example, Freeze-thaw weathering which involves water entering into the cracks and joints and putting pressure and internal force upon the rock weakening the cliff face by widening these joints. repeated freeze-thawing can lead to the creation of talus scree slopes. Carbonation is a type of chemical weathering which involves the slow dissolution of limestone due to rainfall producing calcium carbonate. Plant roots is a type of biological weathering which involves the plants growing into small cracks and fissures in the rock face which causes the rock to break apart. Although this is largely impacted by the climatic conditions, when it occur such as winter storms, it can produce huge rock falls impacting significantly upon both erosion rates and landscape formations
mass movement is described as the downward movement of rock down a cliff slope, often occurring in saturated conditions. The main role mass movement plays within coastal systems is in transferring weathered material down slope, with this their much like with weathering being able to picked upland, used by erosion processes as well as for removal exposing cliff faced and making them more vulnerable. An example of this is rotational slumping which involves rock failure and movement along a curved rock plane. As the more resistant and impermaeable rocks underlies more porous and less resistant rocks such as clays with their rocks becoming saturated leading to their rotational movement over the more resistant rocks often then creating a terranced cliff profile and will leave marks on the landscape which are known as rotational scars. This is seen in Nash Farm in ChristChurch Bay. Another example of mass movement is rockfall which occurs on slopes on a 40 angle where rock fragment breaks away and either drops vertically or bounces down slope. This is then signifcant as it can rapidly change the coastal landscape, exposing large amounts of cliff face increasing rates of erosion as well as then adding sediment/ eroded material into the coastal system but this can be depend on the lithology and the geology present on the coastline
Assess the relative importance of depositional processes along the coast (or along a named stretch of coast?) (12) 3 points
Intro- main depositional process is that of longshore drift which involves… this can be effected by a number of other factors such as tides and wave attack/ prevailing wind direction and deposition itself will only occur when waves lose energy to continue to transport it so not all is transported away by the backswash, and this can also be described through the processes of gravity settling… and flocculation…. they can be seen to be important along the coast but can also be seen other elements are also important
-deposition is important in the formation of depositional landforms, such as spits which form when… and then can create areas of shelter such as lagoons and bays e.g. at Poole harbour where a double spit has occurred. Can also form bars which are where…e.g. at Stuart bay in Devon. Although must be recognised that these depositional processes only occur along drift aligned beaches as long swash aligned there is very little lateral transfer as sediment is transported up and down almost vertically, perhaps showing the shape of coastline also important?
-deposition also important within the sediment cell concept which involves…., areas of deposition can act as potential sources of sediment or sinks, helping to maintain the state of equibrillium sediment cells try to operate, also involving feedback loops… to maintain the sediment budget. Although other factors must also be recognised as being important, such as erosion that are key in producing sediment to be transported as well as overall wave energy?
-other factors are also important in maintaining sediment along a coast, such as the process of plant succession which is where… and plants help to bind sediment etc…. this is also true for salt marshes which also help to…. although do mainly only occur around lagoons and estuaries that form from initial deposition processes and landforms such as spits and bays..?
Explain how the sediment cell concept contributes to the understanding of coastal systems (8) 2 main points
-Sediment cell concept acts as a system made up of sources, transfers and sinks. Theses processes interlink and help to understand how the
coastal system maintains a supply of sediment and why certain areas along the coast may be more susceptible to erosion, for example depending on rock type, the amount of sediment supplied (the source) may mean more sediment is transferred, and onshore/offshore processes such as deposition/erosion also influencing size of sources/sinks, with this all occurring within largely self-contained sediment cells.
there are 11 sediment cells in England and Wales, acting as a closed system to avoid sediment being transferred from one cell to another. the boundaries of the cells are determined by topography and shape of the coastline, with these acting as natural barriers between cells
-although other factors such as wind direction, tidal currents mean there is always likely transfer of sediment between these cells.
explain the contribution of marine erosional processes to the development of this landscape
explain the contribution of coastal deposition to the development of this landscape
