Introduction
The aim of this report is to critique the article Influence of Wave Action and Lithology on Sea Cliff Mass Movements in Central Algarve Coast, Portugal published by Maria M. Bezzera, Delminda Moura, Oscra Ferreira and Rui Taborda in Journal of Coastal Research in 2011.
The article is devoted to the research made by the authors on the topic of the natural processes influencing the rocks movements along the coastline. The main purpose of the initiated research was to determine the relative degree of influence of wave action and lithological type of the rocks on the sea cliff mass movements in Central Algarve Coast in Portugal.
The urgency of the issue studied by the authors is proved by the lack of research on the topic. Although there is plenty of geological research on the erosion of the shoreline represented by the sandy coasts, just a few studies have been devoted to the sea rocks movements due to the technical difficulties in rock formations studying, the high costs of research as well as the relative significance of sandy coasts for the human activity.
However, the researchers warn that the global warming makes a significant impact on the sea level, thus, increasing the probability of the serious shifts in the geological formations on the Earth. In this respect, the coastline is at a high risk of damage. Its damage, in turn, will essentially influence the life and activity at coastal areas.
Furthermore, it can even lead to the catastrophic consequences. “The management of coastal erosion risk will be an increasingly significant issue for the foreseeable future, due to the effects of climate change” (Assessment of Coastal Erosion p.4).
Materials and methods
The research initiated by the article authors was made with the application of the following scientific methods: the method of scientific modeling, the method of comparison, and the hydrodynamic analysis method. The object of the study was the Central Algarve Coast in Portugal. For the purposes of the scientific investigation, the area was divided into five sectors, each of which was tested for the relative susceptibility to the wave action and lithological processes.
There are three major types of waves meeting the shore. They are spilling, breaking, and breaking with trapped air (Wave Erosion par.6).
The authors applied “a numerical wave propagation model (STWAVE) to evaluate differences in breaking wave height and energy along the study area for a set of representative wave conditions and comparison with existing mass movement data” (Bezzerra et al. p.162). The application of the method of the scientific modeling allowed researchers testing the object of research under pre-specified conditions.
In particular, they determined the wave height and the year of its peak using the following metrics: average value, the level of storm threshold, annual storm, 10-y return period storm, and 50-y return period storm (Bezzerra et al. p.164). The various metrics were used in order to decrease the probability of the statistical fault. The simulation of waves was made in order to obtain the measures of the wave heights and energy which were further used for the wave energy density computation and the classification of the coastal area sectors by the average measures obtained (Bezzerra et al. p.164).
Data analysis and conclusions
The correct application of the model required the use of a substantial amount of data. The authors used the 85 mass movements obtained by Marques for the period of 1947-1992. “For the 15.06 km of coastline analyzed, the 85 mass movements occurred between 1947 and 1992 and generated a total volume displaced of 67,561 m3, or 100 m3 per year per kilometer of cliff length” (Bezzerra et al. p. 167).
The results of the wave propagation model application were used to classify each of the five sectors of the investigated coastal area. The following criteria were applied for each sector: cliff coastline length, number of mass movements, total volume displaced, and volume displaced in Miocene carbonate rock, orientation of the coastline, maximum cliff height, geological structure, main system fault, and wave energy (Bezzerra et al. p. 167). The results were presented in the tables and the geological pictures.
The properties of the rock formations play a substantial role in their susceptibility to the wave action influence. “Cliffs’ ability to withstand wave attack varies according to their resistance to erosion, as measured by their compressive, tension (tensile and penetration strengths), and cohesive properties” (Bezzerra et al. p.163).
The erosion is a physical process of the influence of water and wind on the rocks resulting in their gradual devastation. In addition, it is the important factor of the Earth relief formation and change. The coastal erosion is defined as “the detachment of material, transport through the cliff system, deposition on the foreshore and its removal by wave action” (Assessment of Coastal Erosion p.6).
The results of the research allowed the authors making the following conclusion: rock lithology plays an important role in the sea cliff mass movements in spite of the differences in wave heights and energy along the coastline (Bezzerra et al. p.170). In addition, it was found that the frequency of mass movements varies depending on the softness or hardness of the rock structure (Bezzerra et al. p.170). The authors also marked out the resistance to erosion as the important factor of the sea cliffs susceptibility to the movements.
Critique
The article Influence of Wave Action and Lithology on Sea Cliff Mass Movements in Central Algarve Coast, Portugal by Maria M. Bezzera, Delminda Moura, Oscra Ferreira and Rui Taborda represents a valuable contribution to the study of the major geological processes on the Earth including the erosion and mass movements.
The researchers touched upon the problem of harder sea cliffs susceptibility to the wave action and lithology. The previous study was primarily focused on the investigation of the sandy coasts. That is why the article represents a scientific value and uncovers the urgent issue in Geology. It is advised for studying among the students in Geology.
The language used in the article makes it clear and understandable. However, the knowledge of the main physical and geological terms is necessary for better understanding of the methods applied by the authors. In particular, the authors do not give us the definitions of such terms as erosion and coastal erosion. The readers should pay attention to the definition of these basic terms for in-depth understanding.
The conclusions made by the authors were well formulated and supported by persuasive arguments. However, on my opinion, there is lack of the evidence to state that the degree of relative influence of water action and lithology is the same for all rock formations on the Earth. Probably, the additional research in other areas of the planet should be done to prove this.
Overall, the article is rather interesting for studying. It will, undoubtedly, help in the studying of geological processes and can serve as a background for further research.
Works Cited
Assessment of Coastal Erosion and Landsliding for the Funding of Coastal Risk Management Projects. PDF file. 2013. Web.
Bezzera, Maria M., Delminda Moura, Oscra Ferreira and Rui Taborda. “Influence of Wave Action and Lithology on Sea Cliff Mass Movements in Central Algarve Coast, Portugal.” Journal of Coastal Research 27.6A (2011): 162-171. Print.
Wave Erosion and Marine Geology. PDF file. 2013. Web.