Evidence of extreme wave events from boulder deposits on the south-east coast of Malta : storm or tsunami?

Abstract

Introduction: This study investigates the presence of a considerable quantity of boulders observed along a 3.5km stretch of coast situated between Xghajra and Żonqor on the SE coast of the Maltese Islands. The occurrence of such boulders has been associated with extreme wave events such as powerful storms or tsunamis. Studies on boulder deposits have been carried out on coasts that are exposed to varying wave and climatic regimes in different parts of the globe. Some of the studies carried out within the Mediterranean region include the coasts of France, Southern Italy, Greece, Egypt, Algeria and Malta. Conclusions from these studies vary with boulder movement being attributed to both storms and tsunamis. Distinguishing boulder deposits according to the type of extreme events debated and not always straightforward, especially on coasts with a history of tsunami occurrences. However, such studies shed light on the quality and magnitude of wave phenomena which impact on such coasts. The importance of understanding the magnitude and frequency of such phenomena lies in the potential risk that these may pose not just to coastal communities but also to local economies, considering the ever increasing coastal urbanisation and the use of coastal zone by various industries such as recreation, tourism, power generation, trade and port facilities.