Tsunamis boulders on the rocky shores of Minorca (Balearic Islands)

Abstract

Abstract. Large boulders have been found on marine cliffs of 24 study areas on Minorca, in the Balearic archipelago. These large imbricated boulders of up to 229 t are located on platforms that comprise the rocky coastline of Minorca, several tens of meters from the edge of the cliff, up to 15 m above the sea level and kilometers away from any inland escarpment. They are mostly located on the south-eastern coast of the island, and numerical models have identified this coastline as a zone with a high probability of tsunami impact. The age of the boulders of the studied localities range between 1574 AD and recent times, although most of them are concentrated around the year 1790 AD. Although some storm waves might play a role in their dislodging, the distribution of the boulder sites along the Balearic Islands, the degree and direction of imbrication and the run-up necessary for their placement suggest transport from northern African tsunami waves that hit the coastline of Minorca.

Systematic Review Shows That Work Done by Storm Waves Can Be Misinterpreted as Tsunami-Related Because Commonly Used Hydrodynamic Equations Are Flawed

“…Marine weather buoys generally record significant wave height, not the heights of individual waves (e.g., Samayam et al, 2017), so the largest values in wave databases are not maximum wave heights. Unfortunately, many CBD studies either wrongly report buoy data as maximum wave heights or report significant wave heights but treat them as maxima (e.g., Kennedy et al, 2007;Scicchitano et al, 2007;Shah-Hosseini et al, 2011;Engel and May, 2012;Mottershead et al, 2014;Deguara and Gauci, 2017;Roig-Munar et al, 2018. These studies are all well-cited, indicating that this approach, and the underlying misconceptions, are deeply embedded in the community and in the literature.…”

Imbricated Coastal Boulder Deposits are Formed by Storm Waves, and Can Preserve a Long-Term Storminess Record

“…Sustained flow, characteristic of tsunami, is given as a requirement for megagravel imbrication e.g. 2–4 , with suspension transport assumed in some cases 5 ; leading to boulder ridges being interpreted as a signature of tsunami overwash 6 . Erdmann et al .…”

Tsunami Boulders on the Rocky Coasts of Ibiza and Formentera (Balearic Islands)

“…Applying this average value of dissolution rate to the mean depth of the dissolution pans (6.8 cm), results in a time-lapse of 227 years, obtaining an age of 1792 AD for Formentera boulders emplacement [47]. This dating shows similar age than the documentary sources of a tsunami registered in 1756 [35] in the municipality of Santanyí (SE Majorca) and with the data analyzed in boulders by C14 on the coast of Minorca [17].…”

“…The presence of boulders on the rocky coasts of Majorca (the largest of the Balearic Islands) was studied by [11,15,16]. Reference [17,18] analyzed boulders on the coasts of Minorca and Majorca (see Supplementary Materials), applying different equations to distinguish between the boulders associated with storms and boulders associated with tsunamis, and outlining its relation with the trajectories of tsunamis from the N of Africa [19]. In this paper we document, for the first time, the presence of large boulders on the coasts of Ibiza Island (located at the S of the Balearic Islands).…”