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Multi-scale stability analysis at San Pedro Cliff in the Alhambra Cultural Heritage
Published in Renato Lancellotta, Carlo Viggiani, Alessandro Flora, Filomena de Silva, Lucia Mele, Geotechnical Engineering for the Preservation of Monuments and Historic Sites III, 2022
J.A. Fernández-Merodo, R.M. Mateos, J.C. García-Davalillo, J.M. Azañón, C. Novo, R. Castellanza, D. Spizzichino, C. Margottini
The global failure mechanism obtained in the previous local-scale modelling is not representative of the local superficial erosion and scarp retreat observed (Figure 7-right) and recorded by the monitoring. A new numerical analysis is made using the point clouds generated by the TLS scanning performed the 5 July 2017.
Morphogenetic landforms
Published in Richard J. Chorley, Stanley A. Schumm, David E. Sugden, Geomorphology, 2019
Richard J. Chorley, Stanley A. Schumm, David E. Sugden
Inselbergs possibly develop by two mechanisms which frequently merge into each other – as subaerial residuals, or as exhumation features. The first mechanism may produce inselbergs as residuals on more massively jointed or preferentially located rock, remaining either during downwearing accompanying accelerated differential in situ weathering (as has been proposed for parts of south-east Brazil and the Ivory Coast) or by scarp retreat (as King has proposed for parts of southern Africa). The occurrence of structurally controlled inselbergs rising from little-weathered bedrock pediments supports such a mechanism. It has been suggested that, for example, the ‘sugarloaves’ of Rio de Janeiro may be the exposed cores of otherwise fractured rock masses (Twidale, 1982). Figure 18.24 shows how, during folding, a rock mass, although under general compression, develops tension fractures that permit weathering to weaken the rocks surrounding the massive cores. When the weathered rock is eroded, the inselbergs appear as steep-sided residuals on an erosional plain. On the other hand, exhumation mechanisms involve the association of differential deep weathering and surface degradation either concurrently or consecutively (Figures 18.22 and 18.23). The reality of such mechanisms is supported by the observed depths of local weathering in the wet-dry tropics, the fact that domed forms appear to be favoured in some circumstances by subsurface weathering, the existence of weathering or laterite remains on some inselberg summits, and the occurrence of weathered zones surrounding many inselbergs (Figure 18.25). This instance highlights the problems of attempting to relate specific landform assemblages unequivocally to present climates. The inselberg region shown in Figure 18.25 at present has a tropical wet-dry climate (mean annual rainfall approx. 1300 mm in more than eight wet months), yet only 480 km north the mean rainfall is 689 mm in four wet months. Thus there is here a relatively narrow zone of considerable climatic gradient across which climates have oscillated violently between moist savanna (i.e. virtually humid tropical) and semi-arid even during the last few thousand years.
Age and origin of the Cumberland (Inner Sydney) Basin of southeast Australia
Published in Australian Journal of Earth Sciences, 2021
The Woronora Plateau forms the southeast edge of the Cumberland Basin (Figure 1a). The upland is aligned northeast–southwest and runs from Port Hacking in the north to around Shellharbour in the south. The plateau makes up the eastern limb of the Camden Syncline, with the Hawkesbury Sandstone surface rising to the southeast from beneath the cover of Wianamatta Group shales that forms the floor of the Cumberland Basin. The plateau is truncated along its southeast edge by the scarp of the Illawarra Escarpment. This reaches 650–700 m in height (Young, 1980), with cliffs of up to 100–200 m at its northern end (Short, 2007). Despite being very nearly linear for its northernmost 70 km, the escarpment is an erosional feature (Young, 1980), although it is conceivable that it originated by scarp retreat from a new continental edge created by the rifting that began about 84 Ma ago along the eastern edge of Australia (Gaina et al., 1998; Ollier, 1982). The rivers draining the Woronora Plateau all rise within a few kilometres of the escarpment and flow north or northwest down the backslope. Just beyond the southern end of the Woronora Plateau, a surface cut across the Wianamatta Group and the Hawkesbury Sandstone is overlain by the Robertson Basalt of probable Eocene age (Ray, 1986; Wellman & McDougall, 1974). It is likely, therefore, that the surface of the Woronora Plateau was also exposed by this time.