MALLORCA – The Spanish meteorological service AEMET has issued a warning for the Balearic Islands due to the possibility of the weather phenomenon ‘meteotsunami’. The inhabitants of the islands know it as a ‘rissaga‘.
Although the name ‘meteotsunami’ sounds spectacular and perhaps frightening, it is a well-known phenomenon on the islands of Mallorca, Menorca, Ibiza and Formentera. It also occurs in other parts of the world.
En este primer mareograma se observa una oscilación amplia debida a la marea astronómica. pic.twitter.com/8V68R89DjD
— AEMET Medina (@AEMET_Medina) July 24, 2023
It is an extraordinary temporary change in sea level that takes place within minutes, especially in bays and harbours of the Balearic Islands and some parts of the Spanish east coast ‘Levante’. In 2006, a rissaga with variations of up to 4 metres caused extensive damage in the port of Ciutadella in Menorca. A meteotsunami is caused by rapid changes in air pressure that sometimes occur during the passage of a rapidly moving, active squall line.
Sea level fluctuations up to 1 metre
The most common rissagas cause sea level fluctuations of 60 to 100 cm at 10-minute intervals. In some cases, however, the water level can fluctuate by up to 4 metres. This can cause serious problems for boats in the harbour, which can hit the bottom. After a few minutes, the water suddenly flows back into the harbour, which can again cause damage to boats that collide with each other or against the quay.
Y respecto a la climatología, la época del año más favorable es primavera y verano, debido a la mayor frecuencia de entrada de aire cálido. Julio el mes en el que más rissagas se producen. pic.twitter.com/eSYdXx1KJK
— AEMET Medina (@AEMET_Medina) July 24, 2023
Also read: Chance of tsunami in the Mediterranean Sea in the next 30 years “highly likely”
However, it is important to distinguish between a ‘rissaga’ and a tsunami. Tsunamis are caused by geological events such as submarine earthquakes and rissaga is a more localised phenomenon influenced by specific geographic and meteorological factors in an area.
Andalucia introduces anti-tsunami protocol
In other news, Andalucia, with almost 1,000 km of coastline and 500 beaches spread over 62 municipalities, has approved the first emergency plan against the risk of tsunamis in Spain. This comes after an analysis of the real danger that a tsunami could reach Andalucian shores following a major seismic event.
Antonio Sanz, the regional minister of the Presidency and the Interior, described the plan as “unprecedented and absolutely necessary”. The Junta de Andalucía has been working on it for more than two years, with the aim of making the beaches safer and at the same time more attractive. The plan includes a detailed hazard map and a building vulnerability map in the event of a tsunami.
Also read: Spanish bathers startled by mini-tsunami
