Two‐hourly surface change on supra‐tidal rock (Marengo, Victoria, Australia)

Abstract

A traversing micro-erosion meter was used to measure rock surface micro-topography over 40 cm 2 on a supra-tidal cliff face from early morning to late evening in late spring. From 06:00 hours to 22:00 hours the relative heights of 188 coordinates were obtained using the meter at 2-hour intervals, resulting in a data set of 1607 readings. Monitoring shows that rock surfaces are dynamic entities, with significant rise and fall relative to the first measurement at shorter timescales than previously reported. The maximum positive rise between readings was 0·261 mm and lowering was 0·126 mm. The pattern of change did not relate as expected to environmental variables such as temperature or insolation. Rather, the surface showed greater surface change in the early morning and late afternoon. It is hypothesized that this pattern relates to the expansion and contraction of lichen thalli as moisture is absorbed during higher humidity in the morning and late afternoon. The implications of these results for weathering studies are considered.

Cool barnacles: Do common biogenic structures enhance or retard rates of deterioration of intertidal rocks and concrete?

“…Lichen and even microbial biofilms are implicated in short-term (hourly to diurnal timescales) swelling and shrinking of coastal rocks via albedo effects and moisture retention (Gómez-Pujol et al, 2007;Mayaud et al, 2014). And seaweeds have been shown to buffer surface thermal extremes and limit the amplitude of temperature and humidity cycles over diurnal and shorter timescales (Coombes et al, 2013a).…”

Reconceptualising the role of organisms in the erosion of rock coasts: A new model

“…Such studies cover hours (Gómez-Pujol et al, 2007), decades Dornbusch and Robinson, 2011) and larger spatial scales (cmm, meso-scale) and macro-scale (N m; Gómez-Pujol et al, 2006;Swantesson et al, 2006a,b;Cruslock et al, 2010;Naylor and Stephenson, 2010;Dornbusch and Robinson, 2011). This meso to macro-scale of enquiry is broadly comparable to the 'meso-scale' outlined by French and Burningham (2009), a scale at which they argue has an urgent need for predictions of responses of coastal morphodynamics.…”

Rock coast geomorphology: Recent advances and future research directions

“…Researchers have sought to improve quantification and understanding of individual processes. For example, Stephenson and Kirk (2001), , Trenhaile (2006), Trenhaile et al (2006), Gómez-Pujol et al (2007), Porter and Trenhaile (2007) and Hemmingsen et al (2007) have conducted field and laboratory experiments to examine the role of wetting and drying and on the nature and variability of surface expansion and contraction on shore platforms. Research has ranged from field experimental colonisation trials of rock blocks coupled with novel microscopy techniques to laboratory wetting and drying experiments by Kanyaya and Trenhaile (2005).…”