Downwearing rates on shore platforms of different calcareous lithotypes

Moura, Delminda; Gabriel, Selma; Ramos-Pereira, Ana; Neves, Mário; Trindade, Jorge; Viegas, José; Veiga-Pires, C.; Ferreira, Óscar; Matias, Ana; Jacob, José; Boski, Tomász; Santana, Paulo

doi:10.1016/j.margeo.2011.06.002

Cited by 15 publications

(6 citation statements)

References 36 publications

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“…Significant insight has, however, been made at the micro‐scale where the following key mechanisms of erosion have been identified: (1) grain‐by‐grain abrasion (Kirk, ; Blanco‐Chao et al, ); (2) fragmentation of rock facilitated by wetting and drying (Robinson, ; Stephenson and Kirk, ), warming and cooling (Coombes, ; Mayaud et al, ), salt crystallization in rock lattices (Mottershead, ; Stephenson and Kirk, ) and biological activity (Andrews and Williams, ; Naylor et al, ), followed by removal of fragments via hydraulic drag‐and‐lift force, grain wedging (Kirk, ; Stephenson and Kirk, ; Blanco‐Chao et al, ) and impacts (Cullen and Bourke, ). The rate of platform down‐wearing has been shown to be controlled by: (1) rock type (Kirk, ; Stephenson and Kirk, ; Taylor, ; Dasgupta, ; Moura et al, ); (2) elevation with respect to tidal duration distribution (frequency of submergence/emergence transitions) which is observed to link erosion rate to direct wave action (Robinson, ; Foote et al, ), wetting and drying (Kirk, ; Robinson, ; Stephenson and Kirk, ) and biological activity (Torunski, ); (3) slope (Robinson, ); (4) rock structure (Swantesson et al, ); (5) the presence or absence of beach deposits (Robinson, ); (6) biological cover (Coombes et al, ). Erosion rates change through time, with higher rates observed either in summer when higher temperatures increase efficiency of thermal expansion of salt crystals, and wetting and drying (Robinson, ; Mottershead, ; Stephenson and Kirk, , ), or in winter as a result of increased storminess and wave energy delivery to the foreshore (Robinson, ; Foote et al, ; Moses and Robinson, ).…”

Section: Introductionmentioning

confidence: 99%

“…(1) rock type (Kirk, 1977;Stephenson and Kirk, 1998;Taylor, 2003;Dasgupta, 2010;Moura et al, 2011); (2) elevation with respect to tidal duration distribution (frequency of submergence/emergence transitions) which is observed to link erosion rate to direct wave action (Robinson, 1977;Foote et al, 2006), wetting and drying (Kirk, 1977;Robinson, 1977;Stephenson and Kirk, 1998) and biological activity (Torunski, 1979); (3) slope (Robinson, 1977); (4) rock structure (Swantesson et al, 2006); (5) the presence or absence of beach deposits (Robinson, 1977); (6) biological cover (Coombes et al, 2017). Erosion rates change through time, with higher rates observed either in summer when higher temperatures increase efficiency of thermal expansion of salt crystals, and wetting and drying (Robinson, 1977;Mottershead, 1989;Stephenson andKirk, 1998, 2001), or in winter as a result of increased storminess and wave energy delivery to the foreshore (Robinson, 1977;Foote et al, 2006;Moses and Robinson, 2011).…”

Section: Introductionmentioning

confidence: 99%

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Identifying mechanisms of shore platform erosion using Structure‐from‐Motion (SfM) photogrammetry

Swirad

Rosser

Brain

2019

Earth Surf Processes Landf

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Shore platforms control wave energy transformation which, in turn, controls energy delivery to the cliff toe and nearshore sediment transport. Insight into shore platform erosion rates has conventionally been constrained at millimetre‐scales using micro‐erosion metres, and at metre‐scales using cartographic data. On apparently slowly eroding coasts, such approaches are fundamentally reliant upon long‐term observation to capture emergent erosion patterns. Where in practise timescales are short, and where change is either below the resolution or saturates the mode of measurement, the collection of data that enables the identification of the actual mechanisms of erosion is hindered. We developed a method to monitor shore platform erosion at millimetre resolution within metre‐scale monitoring plots using Structure‐from‐Motion photogrammetry. We conducted monthly surveys at 15 0.25 m2 sites distributed across the Hartle Loup platform in North Yorkshire, UK, over one year. We derived topographic data at 0.001 m resolution, retaining a vertical precision of change detection of 0.001 m. We captured a mean erosion rate of 0.528 mm yr‐1, but this varied considerably both across the platform and through the year. We characterized the volume and shape of eroded material. The detachment volume–frequency and shape distributions suggest that erosion happens primarily via removal of shale platelets. We identify that the at‐a‐point erosion rate can be predicted by the distance from the cliff and the tidal level, whereby erosion rates are higher closer to the cliff and at locations of higher tidal duration. The size of individual detachments is controlled by local micro‐topography and rock structure, whereby larger detachments are observed on more rough sections of the platform. Faster erosion rates and larger detachments occur in summer months, rather than in more energetic winter conditions. These results have the potential to form the basis of improved models of how platforms erode over both short‐ and long‐timescales. © 2019 John Wiley & Sons, Ltd.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Identifying mechanisms of shore platform erosion using Structure‐from‐Motion (SfM) photogrammetry

Swirad

Rosser

Brain

2019

Earth Surf Processes Landf

View full text Add to dashboard Cite

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“…Porosity influences the intake and permeability of fluid within the rock and itself increases through chemical (Jin et al., 2011; Navarre‐Sitchler et al., 2013) and physical processes thereby exposing more pore‐surface area to further weathering. Porosity has been shown to correlate well with salt weathering (Yu & Oguchi, 2010), freeze thaw durability (Lindqvist et al., 2007), and down‐wearing rates of shore platforms by weathering processes (Moura et al., 2011). Slake durability is a measurement of the susceptibility to physical and chemical weathering processes, particularly degradation by wetting and drying cycles (Franklin & Chandra, 1972) and has been shown to correlate with carbonate and clay mineral content (Gökceoğlu et al., 2000; Nandi & Whitelaw, 2009).…”

Section: Methodsmentioning

confidence: 99%

A Field Study on the Lithological Influence on the Interaction Between Weathering and Abrasion Processes in Bedrock Rivers

2022

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Lithology is an important control on the efficiency of bedrock incision and thus the pace of landscape evolution. Rock strength is commonly considered the limiting lithologic factor that resists erosion. Yet, rock strength is a dynamic property that oscillates during advection of rock to the channel surface as damaging processes weaken rock and erosion exposes fresh rock. We approach the problem by investigating damage on bedrock surfaces that vary by the frequency they are eroded in channels of different lithologies. Our data set includes measurements of channel slope and width to characterize channel morphology, and Schmidt hammer rebound, P wave velocity, slake durability, and porosity to characterize the mechanical properties of channel surfaces. The average damage accumulation rate of lithologies ranges over 41% of the mean. We find a range of damage patterns among the different lithologies. Local surface damage increases with erosion frequency in channels comprised of coarse‐grained bedrock but decreases with erosion frequency in channels comprised of fine‐grained bedrock. We interpret these patterns to develop from lithological influences on weathering, abrasion, and the threshold of damage to erosion. The cross‐channel damage patterns between channel floors and margins are well correlated with stream power demonstrating links between microstructural rock properties, reach‐scale morphology, and landscape‐scale processes. We conclude that the morphodynamics of bedrock channels are sensitive to the lithological influences on the direction and magnitude of feedback in the coevolution of bedform morphology and the mechanical properties of the surface.

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“…A common result of cliff retreat is the generation of rock platforms, usually less than 100 m wide due to the rapid wave energy dissipation, that prevents the progression of wave erosion and hence limits the extent of such erosional forms (Trenhaile, 1987). Rock weathering and bio-erosive processes are the main mechanisms of rock downwearing (Trenhaile and Porter, 2007;Moura et al, 2011); waves export the resulting products and flatten the surface to the medium sea level through abrasion (Gómez-Pujol et al, 2006;Blanco-Chao et al, 2007).…”

Section: High Rocky Coastsmentioning

confidence: 99%

The complexity of studying coasts: From forms and processes to management

Prieto

2022

CIG

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Coastal environments are characterized by their high dynamism, related to the interaction between marine agents (winds, waves, currents, sea level changes) and continental forms and processes. The present article summarizes the main morphodynamic characteristics of coasts and the resulting environments. Different oscillations of the sea level are considered, depending on their amplitude and frequency: rapid eustatic fluctuations, energetic tsunamis, storm waves and surges, tides and good weather wind waves. Coastal environments are classified in low, sedimentary coasts, including beaches, dunes, barrier islands, lagoons, salt marshes and river mouths, and high, rocky coasts. Management of coastal zones needs a deep knowledge of all the processes involved at the littoral, especially at the local scale, since coastal processes vary rapidly alongshore. At present the integrated coastal management intends to involve different socioeconomic sectors interested in the occupation and use of coasts. Coastal management must include the adaptation of human activities to the natural processes and associated coastal hazards and the protection of coastal values, both of natural and historical-cultural character. Public administrations at different levels should consider the knowledge of the coastal processes at different scales and their potential interaction with human activities in order to design laws and regulations accordingly.

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Downwearing rates on shore platforms of different calcareous lithotypes

Cited by 15 publications

References 36 publications

Identifying mechanisms of shore platform erosion using Structure‐from‐Motion (SfM) photogrammetry

Identifying mechanisms of shore platform erosion using Structure‐from‐Motion (SfM) photogrammetry

A Field Study on the Lithological Influence on the Interaction Between Weathering and Abrasion Processes in Bedrock Rivers

The complexity of studying coasts: From forms and processes to management

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