Non-Destructive Analysis to Investigate the Stone Alterations at a UNESCO World Heritage Site

Abstract

This study concerns the eleven monolithic churches in Lalibela, in northeastern Ethiopia, a UNESCO World Heritage Site and currently the main pilgrimage site in Ethiopia. In 2019, on the initiative of Prime Minister, the French authorities proposed their support in the management on the site of the churches. To do so, the French Development Agency (AFD), in collaboration with the Ministry of Europe and Foreign Affairs and with the support of the Ministry of Culture, granted a feasibility study to examine ways of restoring, conserving, and developing the rock-hewn churches. The objective of the feasibility study conducted was to produce the preliminary technical diagnostics required for the preparation of the comprehensive project to restore, conserve, and develop the site. In order to propose a protection and conservation solution, diagnostics and analysis of the pathology of the rocks were made during two campaigns in November 2019 and November 2020. The rock pathology teams implemented non-destructive and minimally invasive analysis. The complementary methods acquire data from the rock surface and the different forms of differential alteration of the scoriaceous basalt. The objective is to characterize, through comparative analyses, the impact of a protective shelter on the alteration kinetics of the rock. The analysis, coupled with on-site observations, suggests that deterioration linked to liquid water and the persistence of a state of high water content is more damaging than the deterioration risk linked to salt crystallization. As water is the key factor in the very harmful alteration for the conservation of scoriaceous basalt as a heritage material in humid natural environments, it seems useful to fully cover the churches. Doi: 10.28991/HEF-2022-03-02-01 Full Text: PDF