A wave as high as 1.5 meters (5 feet) hit the islands of Mallorca and Menorca during the early morning hours of Monday, July 16.

Published 6 years ago, updated 5 years ago

Meteorological tsunamis or meteotsunamis – locally known as Rissagas – are hazardous long ocean waves, which have the same frequencies and spatial scales as tsunami waves.

However, they are not related to seismic activity, volcanic explosions or submarine landslides, but to atmospheric forcing: pressure jumps, atmospheric gravity waves, frontal passages, squalls, etc. Development of a meteotsunami depends on several factors such as the intensity, direction, and speed of the disturbance as it travels over a water body with a depth that enhances wave magnification. Like an earthquake-generated tsunami, a meteotsunami affects the entire water column and can become dangerous when it hits shallow water, which causes it to slow down and increase in height and intensity. Even greater magnification can occur in semi-enclosed water bodies like harbors, inlets, and bays

Rissagas typically happen several times a year in the region, but many go almost unnoticed. Monday’s however was on the extreme side.

The 1.5m wave hit numerous ports along the coasts of both islands.

Particularly affected in Mallorca were Puerto de Alcudia, Andraitx, Porto Colom, Porto Cristo, and Colonia de Sant Jordi. In Mallorca, Ciutadella suffered flooding and damage. All affected ports saw flooding of beaches, roads, bars, and terraces with beach chairs, boats, and parasols being swept away.

Ciutadella, Menorca, has suffered damage from Rissagas before. The town was damaged by significant waves in both 1984, 2006 and 2013, causing millions of pounds of damage to the harbor and boats.

Fishermen in Alcudia reported that they “had never seen “such a ‘rissaga’ in the bay of Alcúdia”. The water level dropped by one meter in a matter of minutes and then returned flooding the seafront. The Rissaga started at 9.15 hours and lasted about two hours.

The beaches were still relatively empty when the event took place, however, a German tourist walking on the beach at Porto Petro was swept out to sea and died.

Typically during a Rissaga, a sudden rise and fall in sea level occur in a very short time (minutes or even seconds). The following video links of Monday’s event give a good indication of what can happen.

https://www.youtube.com/watch?v=4RSaXtO7NGE

https://www.youtube.com/watch?v=f–mtcOMY98

In Sicily meteotsunamis are known as “marrubbio” and in Malta “milghuba”. In the Canaries, they are known as “Mareas del Pino” because they occur every year coinciding with the festival around September 8. In many other parts of the globe, such as the Sea of Japan and East China, the phenomenon is known as abiki.

The eastern coast of the Adriatic Sea is among the world locations especially endangered by meteotsunamis. The best known was the Great Vela Luka Flood of 21 June 1978 in Croatia, likely the strongest known meteotsunami in the world with wave heights of up to 6 meters.