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On This day – 1st November

1st November 2019 @ 6:06am – by Webteam
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The 1755 Lisbon earthquake

also known as the Great Lisbon earthquake, occurred in the Kingdom of Portugal on the morning of Saturday, 1 November, Feast of All Saints, at around 09:40 local time. In combination with subsequent fires and a tsunami, the earthquake almost totally destroyed Lisbon and adjoining areas. Seismologists today estimate the Lisbon earthquake had a magnitude in the range 8.5-9.0 on the moment magnitude scale, with its epicentre in the Atlantic Ocean about 200 km (120 mi) west-southwest of Cape St. Vincent. Chronologically it was the third known large scale earthquake to hit the city (one in 1321 and another in 1531). Estimates place the death toll in Lisbon alone between 10,000 and 100,000 people, making it one of the deadliest earthquakes in history.

The earthquake accentuated political tensions in the Kingdom of Portugal and profoundly disrupted the country's colonial ambitions. The event was widely discussed and dwelt upon by European Enlightenment philosophers, and inspired major developments in theodicy. As the first earthquake studied scientifically for its effects over a large area, it led to the birth of modern seismology and earthquake engineering.

Earthquake and tsunami

1755 copper engraving showing Lisbon in flames and a tsunami overwhelming the ships in the harbour
The earthquake struck on the morning of 1 November 1755, All Saints' Day. Contemporary reports state that the earthquake lasted between three and a half and six minutes, causing fissures 5 metres (16 feet) wide in the city centre. Survivors rushed to the open space of the docks for safety and watched as the sea receded, revealing a plain of mud littered with lost cargo and shipwrecks. Approximately 40 minutes after the earthquake, a tsunami engulfed the harbour and downtown area, rushing up the Tagus river6 "so fast that several people riding on horseback ... were forced to gallop as fast as possible to the upper grounds for fear of being carried away." It was followed by two more waves. Candles lit in homes and churches all around the city for All Saints' Day were knocked over, starting a fire that developed into a firestorm which burned for hours in the city, asphyxiating people up to 30 meters (100 feet) from the blaze.

Lisbon was not the only Portuguese city affected by the catastrophe. Throughout the south of the country, in particular the Algarve, destruction was rampant. The tsunami destroyed some coastal fortresses in the Algarve and, in the lower levels, it razed several houses. Almost all the coastal towns and villages of the Algarve were heavily damaged, except Faro, which was protected by the sandy banks of Ria Formosa. In Lagos, the waves reached the top of the city walls. Other towns of different Portuguese regions, such as Peniche, Cascais, and even Covilh which is located near the Serra da Estrela mountain range in central inland Portugal, were affected. The shock waves of the earthquake destroyed part of Covilh's castle walls and its large towers. On the island of Madeira, Funchal and many smaller settlements suffered significant damage. Almost all of the ports in the Azores archipelago suffered most of their destruction from the tsunami, with the sea penetrating about 150 m inland. Portuguese towns in northern Africa were also affected by the earthquake, such as Ceuta and Mazagon, where the tsunami hit hard the coastal fortifications of both towns, in some cases going over it, and flooding the harbour area. In Spain, the tsunamis swept the Andalusian Atlantic Coast, nearly destroying the city of Cadiz, killing at least 1/3 of its population.


#Calculated travel times (in hours) for the tsunami waves of 1 November 1755

Shocks from the earthquake were felt throughout Europe as far as Finland and North Africa, and according to some sources even in Greenland, and the Caribbean. Tsunamis as tall as 20 metres (66 ft) swept the coast of North Africa, and struck Martinique and Barbados across the Atlantic. A three-metre (ten-foot) tsunami hit Cornwall on the southern English coast. Galway, on the west coast of Ireland, was also hit, resulting in partial destruction of the "Spanish Arch" section of the city wall. In County Clare there was the creation of Aughinish Island when a low lying connection to the mainland was washed away. At Kinsale, several vessels were whirled round in the harbor, and water poured into the marketplace.

In 2015, it was revealed that the tsunami waves may have reached the coast of Brazil, then a colony of Portugal. Such a hypothesis was raised by reviewing letters sent by Brazilian authorities at the time of the earthquake. These letters describe damage and destruction caused by gigantic waves.

Although seismologists and geologists have always agreed that the epicentre was in the Atlantic to the West of the Iberian Peninsula, its exact location has been a subject of considerable debate. Early hypotheses had proposed the Gorringe Ridge until simulations showed that a source closer to the shore of Portugal was required to comply with the observed effects of the tsunami. A 1992 seismic reflection survey of the ocean floor along the Azores-Gibraltar Transform Fault detected a 50 km-long thrust fault southwest of Cape St. Vincent, with a dip-slip throw of more than 1 km. This structure may have created the primary tectonic event.


This article is from our news archive. As a result pictures or videos originally associated with it may have been removed and some of the content may no longer be accurate or relevant.

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