EQ1 Flashcards
using examples, explain the charactersistics of high-energy coastlines (6)
- more powerful destructive waves for majority of the year with more frequent winter storms,e.g The Atlantic coast
- Erosion is key process and more dominant over deposition, e.g cornwall and North west of scotland
- Erosional Landforms such as headlands and cliffs are more dominant in these coastlines
- Rocky coastline more prevalant than beaches
- High energy coastlines, such as the Holderness Coastline in Yorkshire, have strong erosional processes.
> This is because the backwash is stronger than the wash when waves encroach on the beach/land. This creates a steep beach profile as sediment is removed and carried out to sea.
> A high energy coastline will also have more erosional landforms, such as caves, arches, stacks and stumps.
> High energy coastlines will also typically be more rocky and there will be signs of stress on the cliff face due to high energy erosional processes such as Hydraulic action.
assess the extent to which rates of coastal recession and stability depend on lithology
There are numerous ways in which rates of coastal recession and stability depends on lithology, however other factors can affect the rates too. Lithology refers to the physical characteristics of particular rocks.
Firstly, the rock type affects the rate of coastal recession and stability, there are three main rock types which are igneous metamorphic and sedimentary. Igneous rocks such as Granite and Basalt will erode very slowly due to the crystalline structure, the interlocking crystal create a hard and strong rock, they can also have few joints, so there are limited weakness that erosion can exploit. Metamorphic rocks such as slate and marble have a slow erosion rate as they are also crystalline, they also exhibit a feature called foliation, where crystal are all orientated in one direction and the rock is usually folded and heavily fractures which allows the rock to be exploited to coastal recession. However, Sedimentary rocks such as limestone and sandstone erode much faster due to the rock being clastic, rocks with many bedding planes and fractures such as shale are easily exploited to erosion, so the type of rock has an impact on the rate at which it will cause coastal recession and its stability. Furthermore, the weakness of the rock can influence the rates of coastal recession and stability. Permeable rocks allow water to flow through them and include many sandstones and limestones, however impermeable rocks do not allow groundwater flow and include clays, mudstones and most igneous and metamorphic rocks. Permeable rock will erode much quicker as groundwater flow through rock layers can weaken rocks by removing the cement that binds sediment in the rock. It can also create high water pressure within cliffs, this affects their stability. Water emerging from below the cliff face at a spring can cause surface run off erosion. This will allow the rate of cliff recession to be faster and weaken their stability.
In addition, weathering can also affect the rate of coastal recession and stability. Mechanical weathering breaks down rocks due to the exertion of a physical force, it can proceed with freeze-thaw and salt crystallisation. Any rocks with cracks and fissures or high up cliffs away from salt spray are vulnerable. Chemical weathering involves a chemical reaction and the generation of new chemical compounds such as carbonation, hydrolysis and oxidation, limestone and other carbonate rocks are vulnerable so are igneous rocks and metamorphic rocks that contain silicate minerals. Sandstone, siltstone and shales also often contain compounds that can be oxidised. Finally, there is biological weathering, this often speeds up mechanical or chemical weathering through the actions of plants, bacteria or animals by plant roots or rock boring. This can produce rock falls of cliff tops where there is vegetation and on sedimentary rocks. So, weathering can affect different rock types and allow rates of erosion to be affected.
However, wave processes can affect the rates of coastal recession and stability. Most erosion will occur when waves are at their largest influenced by wind, speed and fetch meaning it has enough energy to pick up sediment and it can hit the cliff face, waves approaching at a 90-degree angle and when tide is high, heavy rainfall and if debris from previous erosion has had time to be removed from the cliff foot. There are four processes of erosion, hydraulic action which affects the heavily jointed sedimentary rocks, abrasions which affects the softer sedimentary rocks, attrition which affects the softer rocks and the solution which affects mainly limestone. So, depending on the wave, this can affect the rates of coastal recession and stability along with lithology.
In conclusion, lithology plays a large part in the rate at which coastal recession happens and the stability, however other factors such as characteristics of the waves at the coast can also be responsible for the recession and stability.
evaluate the view that the process of psammore succession is the most important process in the creation of coastal environments (20)
Succession refers to how a group of plants changes over time. One community of plants is replaced by another as succession develops. The process is especially important on coasts as it creates and stabilises the coastal features which are important to understand the process of psammore succession but there are other contributing factors like geology, erosion and salt marsh development which allow us to the evaluate the process of psammore succession and to view it as another cause for the process.
On a coast where there is a supply of sediment and deposition takes place, specialised plants will begin to grow. These first plants are known as the pioneer species. Vegetation plays an important role in the shaping of coastal landscapes. Many coastlines are protected from erosion by plants, these plants stabilise the loose material and hold it together. Vegetation stabilises the sediment when the roots binds together with the sediment, so it is harder to erode. When submerged, plants growing in sediment provide, a protective layer so that it is not exposed to water moving over it. Plants protect sediment from wind erosion by reducing the wind speed. For example, the plants (sea couch, saltwort and sandwort) in the embryo and fore dunes are specially adapted by having waxy leaves to retain moisture and withstand winds, being low on the ground to avoid strong winds. Also, the plant on a yellow dune is marram grass which is salt tolerant, thrives on being buried by sand. This will lead to a new ecosystem of plants which are in equilibrium with the environment and there are no new species, as soil is built up inland, stabilising the dunes and therefore climax vegetation occurs as there is no new supply of sediment.
However, Vegetation succession does play a key role in the creation of a saltmarsh. The succession of vegetation plays an important role at the beginning and end of the saltmarsh formation. The succession of vegetation at an early-stage acts as an obstacle which binds the sediment. An example of this early vegetation is blue-green algae. Without vegetation here, the saltmarsh would be unable to grow upland any further as the silt would be too fine to settle and bind by itself. Furthermore, succession of vegetation continues, getting plants to grow which are bigger and hardier and eventually the saltmarsh builds the sediment up. Without the obstacle of vegetation this wouldn’t be possible. Pioneer species, Halophytes and marsh grass is much thicker species of vegetation that allow for wave energy to slow down and this results in the increased deposition of silt and sediment. This repetition of succession and vegetation domination mean that plants establish the salt marsh and can later grow above tidal levels. Therefore, plant succession is very important in the formation of a salt marsh
Additionally, Geology and erosion are also important factor and made some contributions to the coast landscape. The geology at the coast affects the speed at which it erodes. Rocks like igneous are crystalline, resistant and impermeable meaning water cannot pass through. Other rocks like sedimentary are formed in strata and they are permeable. Therefore, geology is an important aspect of coastal landscape not only psammosere succession which only creates sand dunes and salt marshes. High-energy coastlines have very powerful waves. The rate of erosion is higher than the rate of deposition and an example of this is in Cornwall and northwest Scotland. Low-energy coastlines have less powerful waves. The rate of deposition is higher than the rate of erosion. Some examples are Lincolnshire and Northumberland; therefore, erosion plays a large role in the shaping of the coastline.
Overall, vegetation succession is vital for saltmarshes, sand dunes to form, however for this process to even begin deposition and erosion is require and plays a key role throughout and without it salt marshes and sand dunes and other coastal landforms would cease to exit.
Explain the problems involved with classifying coastlines
Coastlines can be classified in 4 main ways, their geology, level of energy, balance of deposition and erosion, and changes in sea level. The main problem with classifying coastlines is that many coastlines have features that are common for a mixture of both low energy coastal environments as well as higher energy environments. For example, the rocky coastline along Cornwall also has landforms such as beaches and estuaries that are usually associated with environments where deposition is more common. This can also be seen around the southern coast which is predominantly a low energy environment yet still has many steep erosional cliffs.
-A further reason it is hard to classify coastlines is due to how coastlines often change depending on factors such as the seasons and climatic conditions, that can play a large role in the processes present at any given time. For example, the Holderness coastline is mainly a low energy environment however often experiences high energy storm conditions during the winter and s short term erosional processes occur, often then leading to erosional landforms such as the headlands at Flamborough Head. This can also be seen in cornwall which although usually experiences high energy and powerful waves, estuaries still form in more sheltered areas. It can also be said that defining coastlines to be more submerging or emergent is also complex, with often different landforms occurring and again at times these just being temporary and short term.
Explain some factors that create an erosional coastline (4 main factors)
Rock hardness- softer and uncemented sediment and rock more vulnerable to cliff retreat e.g. boulder clay along Holderness
-Geological orientation- Discordant coasts have different rates of erosion resulting in headlands + bays, e.g. Eastern Dorset coast of Isle of Purbeck
Wave type- Destructive waves are stronger and therefore when water is driven into cracks in rocks it can compress air and cause blasts (Hydraulic action)
-Erosional processes- e.g hydraulic action/abrasion can operate together with subaerial processes
-Rock layers- can cause different levels of resistance and rates of erosion
Explain how geological structure affects the development of coastal landforms (6) - 4/5 points
Geological structure refers to concordant or discordant coastlines, as well as lithology and rock structure
-concordant coasts are where geoglogy runs at parallel to coast and has landforms such as coves (lulworth cove) and dalmation coastlines
-depositional landforms such as spits and bars more likley on concordant coasts due to longshore drift more operative
-discrdant coastlines where alternating bands or geology run at right angle to coast and landforms such as headlands and bays more prominent due to the variations in rock resistance
-cliff profiles also influenced by joints and bedding planes
Explain how vegetation can bring stability to low-energy environments (6)
Vegetation can be seen to play an important role in supporting the development of sandy coastlines, helping to stabilize sand dunes to prevent recession. Sand dunes are colonized by vegetation in plant succession, involving different types of plants. Embryo dunes and fore dunes are colonized by plants such as sea rocket that have deep binding roots that can tolerate salt water, then yellow dunes are colonized by marram grass and then heathers are found on grey dunes further from the shore. These first plant pioneer species modify the environment, adding nutrients to the sand and then creeping plants with more leaf cover help dunes to maintain moisture. This therefore encourages more plants to grow and help stabilize the sand dunes.
-This can be seen to be important within low-energy environments as plants help to trap the sand that would otherwise be transported away by winds and long shore drift. By the process of plant succession this creates a climatic climax community, meaning that as the environment continues to be changed over time by the plants, it creates a different climate allowing plants to remain and so keeping sand dunes stabilized.
