1,2,3,2,3- 1Department of Physics. Universidad de Jaén, 23071 Jaén, Spain (jamoleon@ujaen.es, aontiver@ujaen.es, egimenez@ujaen.es)
- 2Centro de Estudios Avanzados de la Tierra y el Medio Ambiente (CEACTEMA), Universidad de Jaén, 23071 Jaén, Spain
- 3Instituto Andaluz de Geofísica. University of Granada, 18071 Granada, Spain
- 5Department of Cartographic, Geodesic and Photogrammetry Engineering. University of Jaén, 23071 Jaén, Spain (maurena@ujaen.es)
Volcanic pyroclastic deposits (tephra) constitute complex granular systems whose macroscopic geomechanical stability is closely linked to microscopic interfacial forces. In the ash fraction from tephra, cohesion is heavily influenced by surface free energy components and their response to environmental parameters like pH and ionic strength. This study evaluates the surface thermodynamic properties of four reddish pyroclastic tephra samples—known as Almagres—collected from distinct geological context of Deception Island (Antarctica), labeled SPLD(5), SPLD(9), SPLD(19), and SPLD(25). To unravel the underlying physicochemical mechanisms governing their cohesion, the surface free energy components were determined and interpreted quantitatively using the Van Oss-Chaudhury-Good theory
The experimental results reveal a pronounced thermodynamic heterogeneity among the samples, reflecting variations in their mineralogical and alteration states. Applying the Van Oss framework allowed for the decoupling of apolar Lifshitz-van der Waals (γLW) and polar Lewis acid-base (γAB) interactions. Sample SPLD(5) exhibits a strictly monopolar electron-donor behavior, characterized by a significant basic component γ- = 66.00 mJ/m2 but completely lacking an acid contribution γ+ = 0.00 mJ/m2, resulting in a null polar component γAB = 0.00 mJ/m2 and a total surface energy γTot equal to its apolar value 43.40 mJ/m2. Conversely, sample SPLD(25) demonstrates a highly active bipolar (amphoteric) character, yielding the highest total surface energy γTOT = 100.53 mJ/m2 and a remarkably strong electron-acceptor component (γ+= 23.40 mJ/m2.
These surface energy variations directly dictate the samples' interaction with the interstitial aqueous phase, as quantified by the work of adhesion to water Wa. The water affinity ranges from a minimum of 126.9 mJ/m2 for the moderately polar SPLD(19) to a maximum of 159.7 mJ/m2 for the highly polar SPLD(25). It is concluded that the varying polar and apolar surface profiles of these Almagres crucially modulate interparticle capillary bridges and adhesion under shifting geochemical conditions. Furthermore, the insights gained from this unaltered polar analog provide a valuable predictive framework for Mediterranean anthropized volcanic systems, where similar fluid-particle interactions dictate geomechanical risks in active volcanic edifices.
How to cite: Moleón, J. A., Ontiveros, A., Giménez, E., Abad, M. I., Ureña, M., and Sánchez-Gómez, M.: Surface Free Energy Characterization of Reddish Volcanic Tephra (Almagres) from Deception Island: Implications for Granular Cohesion, 19th Plinius Conference on Mediterranean Risks, Murcia, Spain, 6–9 Oct 2026, Plinius19-64, https://doi.org/10.5194/egusphere-plinius19-64, 2026.
