Issue link: https://maltatoday.uberflip.com/i/1544378
13 maltatoday | SUNDAY • 12 APRIL 2026 NEWS JAMES DEBONO jdebono@mediatoday.com.mt THE historic Lunzjata Chapel perched on a rocky promonto- ry in Siġġiewi, serves as a stark reminder of the fragile relation- ship between Malta's cultural heritage and its volatile geology. Long plagued by instability, the 15th century chapel has undergone repeated cycles of damage and reconstruction following major earthquakes in 1693, 1856, and 1923. However, the most pressing threat today is not a sudden seismic event but a slow, relentless process of ground displacement that is gradually deforming the struc- ture. This information emerges from a new study entitled Ac- tive Spreading At Maltese Her- itage Sites: Unravelling Instabil- ity Mechanisms Via Integrated InSAR, Photogrammetry, And Geotechnical Analysis. The re- search published in the jour- nal Catena (Volume 268, 2026) was led by Giona Bucci Mon- ica of the University of Malta, alongside Alfredo Rocca, Adri- an Mifsud, Christian Schem- bri, Colica Emanuele, Veronica Mercuri, Daniel Fenech, Chris- topher Gauci and Aaron Mi- callef. The multidisciplinary team combined satellite-based Inter- ferometric Synthetic Aperture Radar (InSAR) with drone- based Structure-from-Motion photogrammetry and geotech- nical analysis to investigate in- stability at key heritage loca- tions. Scientists involved in the study documented that the Lunzja- ta Chapel displays transversal cracks across its structure, ex- tending from ground to roof level. These fractures indicate that the building's foundation is undergoing longitudinal ex- tension and outward rotation toward the valley. The damage is consistent with gradual slope movement rather than abrupt structural failure. Advanced satellite monitoring quantified this instability. The research shows that the chapel exhibits displacement velocities between 7.6mm and 17.6mm per year, with cumulative movements reaching as much as 72mm during the observed period. These shifts are not constant. Geotechnical sensors identified a consistent correla- tion between total displacement and rain, suggesting a seasonal cycle. The ground tends to move toward the slope during hot, dry periods and retract slightly during wetter months. Despite these minor retractions, the process is cumulative, gradual- ly undermining the structural integrity of the masonry vaults. Ongoing restoration works currently underway at the chapel confirm the structural concerns noted in the study. The restoration of the Lunzjata Chapel next to the Laferla Cross in Siġġiewi began in October 2023 under an agreement be- tween the government and the Archdiocese of Malta. Initially expected to finish within a year, the project missed its October 2024 deadline after structural problems emerged once works started. The science behind the threat The underlying mechanism is a geological phenomenon known as lateral spreading. Malta's landscape is charac- terised by a "layer cake" stra- tigraphy, where a heavy layer of Upper Coralline Limestone sits atop a thick, impermeable layer of Blue Clay. Rainwater infiltrates the porous limestone until it reaches the clay inter- face, where it accumulates. This causes the clay to swell and lose strength. Under the weight of the limestone plateau, the sof- tened clay is squeezed outward, creating a self-sustaining cycle of plateau instability that is dif- ficult to arrest. Over time, this process forms deep fissures parallel to cliff edges, eventual- ly leading to the detachment of large rock blocks. While the Lunzjata Chapel faces one of the most complex challenges due to its position on an active landslide, the study also points at the significant risks at the Madonna tal-Aħrax monument in Mellieħa. Situat- ed near a precarious cliff edge, the site is threatened by erosion of the underlying Blue Clay. Us- ing high-resolution 3D model- ling, the researchers identified approximately 173,000 cubic metres of rock currently at risk of mobilisation. Popeye Village and Gnejna Tower Other historically and cultur- ally significant locations men- tioned as susceptible to these spreading processes include Popeye Village, the Ġnejna Tower, and various sites along the northwest coast of Malta and Gozo. The study identifies Popeye Village at Anchor Bay as par- ticularly vulnerable because the coastal fringe shares the same limestone-over-clay geology. In this setting, lateral spread- ing continues to exert pressure on the landscape, gradually in- creasing the risk to structures located near cliff edges. To safeguard these landmarks, the authors propose several recommendations. For monu- ments such as the Madonna tal- Aħrax statue, researchers pro- pose relocating the structure further inland—considered the most practical long-term safe- guard against cliff collapse. In contrast, permanent structures like the Lunzjata Chapel require ongoing geotechnical reinforce- ment, including stabilisation and underpinning to counteract sliding ground. In 2023, the Planning Author- ity approved relocating the Tal- Aħrax statue a few metres in- land to address geological risks identified near its original site. However, further instability identified through satellite im- agery studies conducted by the University of Malta's InSAR. SPREAD project revealed the need for a safer location. Supported by IPAS+ grants, this project tracked geological movement between 2011 and 2015 and identified displace- ment velocities of up to 10.2mm per year in some areas. During dismantling works, the original masonry pedestal was discov- ered beneath the concrete cas- ing. The authors of the latest study advocate a multi-disciplinary approach that integrates con- tinuous satellite monitoring with ground-truth validation from geotechnical sensors. Such a framework, they argue, provides public authorities with actionable knowledge to pro- actively monitor and protect Malta's historic landscape be- fore the slow march of lateral spreading results in irreparable loss. Siggiewi's Lunzjata Chapel near Laferla Cross threatened by ground movement Research finds geological movement is main risk for Lunzjata Chapel and other vulnerable coastal landmarks such as Popeye Village at Anchor Bay The Lunzjata Chapel near the Laferla Cross is currently undergoing restoration works but it has been identified as being at risk because of ground movement (Photo: Restoration and Preservation Department/FB) Popeye Village (left) is also vulnerable to geological movement