A sizeable part of the seaward side of the iconic Azure Window in Dwejra has collapsed in recent days, widening the opening in the process.
A deep fissure had long been visible on the side of the structure where the collapse took place.
Natural arches such as the Azure Window are formed through erosion, with a weakness in the rock ending up as an opening which widens over time. In the Dwejra arch’s case it resulted in what is arguably Gozo’s most renowned landmark.
But the same natural process that created the Azure Window will also, eventually, lead to the arch’s demise, either through continued erosion or through a collapse. Such collapses are far from unprecedented elsewhere in the world: A famous natural bridge in the Caribbean island of Aruba had collapsed in 2005, for instance.
Evidence that significant erosion has taken place in a relatively short time at the Azure Window can be found in the 1981 film Clash of the Titans, which features the arch prominently.
In the film, the Coralline Limestone layer showed little sign of erosion, with the part whose underside was exposed to the elements practically as thick as the parts protected by the underlying rock. However, evidence that erosion is taking its toll is now all too clear, given the present difference in thickness between these parts.
But can the arch be saved?
When contacted by this newspaper, geologist Peter Gatt explained that the site required the study of the structural geology. Such a study would look into, among other things, existing fissures and their orientation, as well as the different rock strata present.
The arch itself was created because of the different nature of the two main rock layers. The thicker lower layer is more brittle than the top layer, which forms the arch, and as a result the lower layer is more prone to extension cracks, he noted.
Only through such a study could preservation efforts properly take place, Mr Gatt said.
A study did take place a few years ago. In 2006, the Gozo Ministry had commissioned Bureau Veritas to carry out a geological study over concerns that the collapse of the arch would be detrimental to the island’s tourism. The findings of the study were not widely publicised, although on their website, Bureau Veritas note that the proposals included carrying out work from the top of the arch to save costs and to ensure workers’ safety.
Nevertheless, Mr Gatt shed doubts about whether a proper study had taken place of the site. If it was, he argued, its findings would have been made public and open to the scrutiny of other geologists. Moreover, the recent collapse of the rock slab could have been predicted if a proper study was carried out, and the safety of tourists visiting the arch would have been assured.
He observed that the most pressing issue was not the erosion of the top part, but the widening of the sides of the arch, which increased the span of the arch and that made its collapse more likely. The latest collapse, he remarked, was not likely to have affected the situation, as the collapsed section was only partly supporting the bridge – but a future collapse of remaining rock slab may endanger the arch’s integrity.