Blocs amb origen tsunamític a les costes rocoses del Nord-est de Mallorca (Illes Balears)

[cat]Les costes rocoses del Nord Est de Mallorca, Illes Balears, presenten acumulacions de blocs de mida mètrica que han estat transportats terra endins per forts fluxos hídrics de tsunamis i/o tempestes. Aquests blocs es disposen tant de manera individual com en agrupacions imbricades, sense arribar a formar cordons ben definits, a alçades que van de 1 a 15 m s.n.m i a distàncies terra endins fins als 55 m. La majoria dels blocs són angulosos i el seu pes oscil·la entre 3,5 i 24,5 T. Aquest treball presenta 5 àrees d’estudi on s’han realitzat l’anàlisi morfomètric dels blocs i s’han aplicat equacions per determinar les columnes d’aigua necessàries pel seu transport baix tres supòsits diferents: blocs submergits, blocs subaeris i blocs condicionats per juntes.[eng]The rocky shores of the NE Mallorca (Balearic Islands) have accumulations of boulders that have been transported inland by strong water flows from tsunamis and / or storms. These blocks are arranged both individually and in groups, sometimes with an imbricated setting. They are located at heights ranging from 1 to 15 m and distances up to 55 m inland. Most boulders are angular and its weight varies between 3.5 and 24.5 T. This paper shows the block morphometric analysis of five study areas and determines water columns needed for transportation under three different scenarios: submerged blocks, subaerial blocks and joint bounded blocks

Block and boulder accumulations on the southern coast of Crete (Greece): evidence for the 365 CE tsunami in the Eastern Mediterranean

The Eastern Mediterranean is one of the most seismically active regions in Europe. Crete, located in the centre of the Eastern Mediterranean, should experience tsunamis resulting from large magnitude earthquakes or volcanic eruptions. At three locations boulders were observed that may relate to tsunami or storm events. At Lakki, the size of the boulders slightly favours a tsunami origin for deposition. By contrast, at Kommos boulder size and geomorphology is consistent with storm parameters in the Mediterranean. The most compelling evidence for tsunami transport is found at Diplomo Petris, where a lithologically varied grouping of large boulders (≤ 690 t) is exposed at sea level. The calculated storm wave heights (15 m) required to transport the observed boulders significantly exceeds winter averages; therefore, these accumulations are interpreted as tsunami deposits. Radiocarbon dating of encrusting biological material was undertaken to constrain periods of boulder motion. Encrustations from Diplomo Petris and Lakki pre-date the 365 CE earthquake suggesting that this event transported the largest boulders; the first time boulder deposits have been identified on Crete from this tsunami. Therefore, these data are important for developing local and regional hazard assessments but also to inform numerical models of tsunami propagation in the Mediterranean

Blocs amb origen tsunamític a les costes rocoses del Nord-est de Mallorca (Illes Balears)

The rocky shores of the NE Mallorca (Balearic Islands) have accumulations of boulders that have been transported inland by strong water flows from tsunamis and / or storms. These blocks are arranged both individually and in groups, sometimes with an imbricated setting. They are located at heights ranging from 1 to 15 m and distances up to 55 m inland. Most boulders are angular and its weight varies between 3.5 and 24.5 T. This paper shows the block morphometric analysis of five study areas and determines water columns needed for transportation under three different scenarios: submerged blocks, subaerial blocks and joint bounded blocks. Key words: boulder morphometry, Mallorca, rocky coast, storms, tsunamis