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Bonomo, et al., Evaluation of soft limestone degradation in the Sassi UNESCO site (Matera, Southern Italy): Loss of material measurement and classification, Journal of Cultural Heritage (2019), https://doi.org/10.1016/j.culher.2019.07.017 ARTICLE IN PRESS G Model CULHER-3646; No. of Pages 11 Journal of Cultural Heritage xxx (2019) xxx–xxx Available online at ScienceDirect www.sciencedirect.com Original article Evaluation of soft limestone degradation in the Sassi UNESCO site (Matera, Southern Italy): Loss of material measurement and classification Agnese Emanuela Bonomo a,∗ , Antonio Minervino Amodio b , Giacomo Prosser a , Maria Sileo c , Giovanna Rizzo a a Department of Science, University of Basilicata, Via dell’Ateneo Lucano 33, 85100 Potenza, Italy b Department of Biosciences and Territory, University of Molise, C. da Fonte Lappone, 86090 Pesche, Isernia, Italy c Institute for Archaeological and Monumental Heritage, National (Italian) Research Council (CNR), C/da Santa Loja s.n.c., 85050 Tito Scalo (Potenza), Italy a r t i c l e i n f o Article history: Received 15 January 2019 Accepted 22 July 2019 Available online xxx Keywords: Building stone Degradation Cultural heritage Gravina Calcarenite 3D model Structure from Motion a b s t r a c t Soft limestone degradation is the main problem in the old district of Matera (Sassi), a rupestrian set- tlement excavated and built in the Pleistocene Gravina Calcarenite, which has been recognized as a UNESCO heritage site since 1993. The Gravina Calcarenite outcrops in a large area in the Apulian fore- land, onlapping the Cretaceous Altamura limestone. It can be divided in two main typologies, the first one characterized by the predominance of bioclastic components and the second one mainly consisting of lithoclastic grains. All Sassi are built and excavated in this soft stone that gives a unique aspect to the town. Unfortunately, the decay of calcarenite materials is very fast and the calcarenite constructions are now in a bad state of conservation. In this work, we present a new method for the classification and the quantitative estimation of material loss in degraded natural stones by using Structure from Motion (SfM) and image analysis techniques. In detail, degradation patterns were described on 250 fac ¸ ades of Matera Sassi by using the International Council on Monument and Site – International Scientific Commit- tee for Stone – ICOMOS-ISCS atlas. The peculiar decay morphologies have been related to the extent of material loss, especially with alveolization patterns that develops on the 76% of the fac ¸ ades. The relation- ships between the identified decay patterns and the lithological features were discussed, highlighting the higher susceptibility of bioclastic calcarenite respect to the lithoclastic type. Following this analysis, five stages of decay related to loss of material were determined and quantified. The proposed approach represents a new and easy method for evaluating the degradation stage of ancient buildings and for better assessing the long-term survey and the maintenance of stone monuments. © 2019 Elsevier Masson SAS. All rights reserved. 1. Introduction and research aims Impressive stone monuments, such as sculptures, buildings or entire towns, represent a complex and diversified artistic, scien- tific and historical archive of a community and a territory, often strictly connected with the natural landscape and the geomorpho- logical features. Stone damage of monuments is an irreversible loss of cultural heritage, so that the scientific community enhanced the efforts towards their conservation all over the world [1]. All kind of rocks that have been physically altered by humans could be defined cultural or architectural stones including megalithic monuments, rupestrian arts and settlements that need to be ∗ Corresponding author. E-mail address: agnese.bonomo@unibas.it (A.E. Bonomo). preserved during time [2]. Monumental stones are among the old- est and most vulnerable cultural heritages because these are largely exposed to natural and anthropogenic environmental agents and subjected to the degradation responsible for visible and some- times irreparable damages [3]. Degradation affects monuments by natural processes, including weathering and thermal stress, or by anthropic processes, including pollution, vandalism and unsuitable restoration. The intensification of both climate changes and air pol- lution is progressively increasing the degradation of built heritage [4,5] with a great increase of decay processes strictly connected to the composition of building stones [6], as e.g. superficial erosion and salt crystallization [7–10]. Reviewing the current literature, the studies of degradation processes are mainly based on qualitative and descriptive anal- yses. The need of a proper standardization of damage analysis led to the institution of international and national commissions https://doi.org/10.1016/j.culher.2019.07.017 1296-2074/© 2019 Elsevier Masson SAS. All rights reserved.