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The Tsunami Phenomenon

Occurrence of Tsunamis

Occurrences of Tsunamis in the Atlantic Ocean

Tsunamis in the Atlantic

Intensive research following the tsunami catastrophe of 2004 showed that many other coastlines are also in danger of tsunamis. Thus the Atlantic coast and the Mediterranean coast are not safe from tsunamis and therefore must be better protected. Few tsunami catastrophes occur in the Atlantic in comparison to the Pacific. The tsunamis at Lisbon and at Puerto Rico were up to now the largest tsunami catastrophes and thousands of people lost their lives.

Map of historical occurrences of Tsunamis in the Atlantic

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Possible tsunami dangers in the Atlantic

La Palma Tsunami

Islands of volcanic origin, such as the Canaries, have an especially large potential for triggering a tsunami. That the Canaries constitute a danger was shown 300 000 years ago when a part of the island El Hierro slid into the sea, triggering a mega-tsunami which carried rocks as high as a house for many hundreds of metres into the interior of the east coast of what is today the USA. The danger of a similar island collapse is seen by scientists particularly at the island of La Palma in the Canaries. Here, following a volcanic eruption in 1949 almost half of the mountain range of 20 km moved westwards towards the sea, leaving a large tear in the volcanic basalt. In the event of a fresh eruption, a huge part of the volcano could loosen itself due to differences in the types of rock and diverse water deposits within the now active volcano. As a result, the densely populated east coast of America would be massively threatened. According to a computer simulation by Stephen N. Ward and Simon Day, a tsunami (purple-red on the graphics) would rush across the Atlantic if the slopes of the Cumbre Vieja.volcano were to collapse into the sea.

Simulation by Stephen N. Ward and Simon Day

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Table of known Tsunami catastrophes in the Atlantic

The greatest Tsunami catastrophes worldwide – an overview

09.07.1956	Greece	Mediterranean Sea, Greece, Amorgos Island, Aedean Islands	7,5	20,00 m	50
11.10.1918	USA	USA, Puerto Rico, Mona Passage, Dominican Republic	7,5	6,00 m	116
01.11.1755	Portugal	Portugal, Lissabon, United Kingdom, Spain, France, Morocco, Haiti, USA, Cuba, Martinique, Dominica	9,0	12,00 m	60.000
29.09.1650	Greece	Mediterranean Sea, Greece, Thera Island, Santorini	k. A.	16,00 m	k. A.

Source: National Geophysical Data Center - Tsunami Event Database

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Greatest known Tsunamis of the Atlantic region

11 October 1918, Puerto Rico: On 11 October 1918 an earthquake of 7,5 on the Richter scale occurred in the Mona Passage west of Puerto Rico. The earthquake created a tsunami that grew to 6 metres and caused huge destruction along the western and northern coast of Puerto Rico. The tsunami caused the loss of 116 lives and physical damage amounting to 29 million dollars.

1 November 1755: The Portuguese capital of Lisbon and its inhabitants were particularly badly hit by an earthquake that occurred in the eastern Atlantic Ocean. Two thirds of the city was destroyed from resulting fires. The people seeking refuge from the flames on the banks of the Tejo River were surprised by huge flood waves produced by the earthquake. Some 60 000 people lost their lives. The waves were even observed in Ireland and on the other side of the Atlantic on the Lesser Antilles. On the coastline of the Madeira Islands the waves still had a height of 15 metres.

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Sources, follow-up links:
Information about terms, causes, characteristics, occurences, prevention and list of past tsunamis (www.en.wikipedia.org)
Archives of tsunamis photographs (www.tsunami.org)
Details of the largest historical tsunamis (www.teachervision.fen.com)

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