1755 Lisbon earthquake

On the morning of 1 November 1755, All Saints' Day, a massive earthquake beneath the Atlantic off south-west Iberia, followed by a tsunami and fire, all but destroyed Lisbon, the capital of Portugal. Perhaps 30,000 to 40,000 people died in the city, with thousands more in Morocco and elsewhere. The disaster shook the confidence of Enlightenment Europe, prompted one of the first planned modern city centres, and is often seen as the starting point of scientific seismology.

The earthquake struck at around twenty to ten in the morning, while many residents were at Mass for the holiday. Witnesses said the shaking lasted between three and a half and six minutes, opening wide cracks in the streets. Modern estimates put its magnitude at 7.7 or more, with the epicentre at sea some 200 kilometres west-south-west of Cape St Vincent. Survivors who fled to the waterfront saw the harbour drain away; about forty minutes later a tsunami surged up the Tagus into the lower town, followed by two further waves. Holiday candles burning in houses and churches were toppled, and the fires that followed merged into a firestorm that burned for hours.

The Algarve coast in southern Portugal suffered severe damage, as did Madeira, the Azores, Cádiz and Portuguese-held and former Portuguese towns in North Africa. Tremors were reportedly felt as far away as Finland. The tsunami crossed the Atlantic to the Caribbean, struck Cornwall and the west coast of Ireland, and, according to letters rediscovered in 2015, reached Brazil.

Of Lisbon's roughly 200,000 inhabitants, an estimated 30,000 to 40,000 died; one estimate for Portugal, Spain and Morocco together is 40,000 to 50,000. Around 85 per cent of the city's buildings were destroyed. The riverside royal palace was lost along with its library of some 70,000 volumes, paintings by Titian and Rubens, and archives recording the voyages of Vasco da Gama and other navigators. The new opera house, the main churches and the great All Saints hospital, where hundreds of patients died, were wrecked or burned. One study puts the economic damage at a third to a half of Portugal's annual output.

King Joseph I and his court survived because they had left the city that morning; the king afterwards refused to live in masonry buildings and moved the court into tents on the hills at Ajuda. His chief minister, Sebastião José de Carvalho e Melo, remembered as the Marquis of Pombal, took charge. Soldiers cleared bodies, many of which were buried at sea, and gallows were raised against looters. Within weeks the royal engineer Manuel da Maia offered plans for reconstruction, and the boldest was chosen: the old lower town was levelled and replaced with a grid of broad, straight streets and large squares. Its buildings were among the first in Europe designed to resist earthquakes, tested with models shaken by marching troops. The Baixa Pombalina still defines central Lisbon.

That a devout Catholic city was ruined on a holy day provoked anguished debate about divine providence. Voltaire wrote a poem on the disaster and used it in Candide to mock the belief that this is the best of all possible worlds. Jean-Jacques Rousseau blamed the scale of the deaths on crowded city life, and the young Immanuel Kant published three texts in 1756 seeking natural causes for earthquakes. Pombal's government also sent a questionnaire to every parish asking how the shock had been felt; the answers, still kept in the national archive, let modern scientists reconstruct the event.

Our 1715 and 1783 maps show the Kingdom of Portugal and the wider Portuguese Empire, including Brazil, which the tsunami reached.