The 1755 earthquake
The earthquake of 1 November 1755 began shortly after 09:30 and destroyed Lisbon’s Baixa, together with the tsunami and the fire that followed. On the Terreiro do Paço it brought down the royal palace and the opera house. Between 10,000 and 30,000 people died, and today’s square was built as part of the Baixa Pombalina.
Updated
What happened on the morning of 1 November 1755
Shortly after 09:30, the ground shook for 6 to 7 minutes. Then came the tsunami, which swept the bank of the Tagus, and a fire that burned a third of the city.
It was All Saints’ Day. José Joaquim Moreira de Mendonça, who lived through the earthquake in Lisbon, wrote that the sky was clear and that the shaking began shortly after half past nine. In the second minute the buildings began to fall. The shaking lasted 6 to 7 minutes, with two short pauses, and dust covered the city.
Many people fled to the Terreiro do Paço and to the riverbank, where there were no buildings. The river drew back and laid bare its bed. Then it came back in three large surges and several smaller ones, which ran up the streets and swept away people and boats. The Cais da Pedra, a large quay to the east of the Terreiro do Paço, disappeared with the people who had taken shelter on it.
Hearths and candles in the fallen houses set the timbers alight. According to Moreira de Mendonça, the fire burned a third of the city, in its most crowded part, with narrow streets and houses of four to six storeys.
How high was the tsunami in Lisbon?
In Lisbon the wave was about 5 metres high. The water came 250 to 350 metres in across the Terreiro do Paço, to about where the arch stands today.
At the Bugio tower, at the mouth of the Tagus, the water rose nearly 5 metres and the garrison had to retreat to the top of the tower. The captain of a ship about 300 metres from the shore measured a rise in the river of about 6 metres.
What the earthquake destroyed on the Terreiro do Paço
Everything on the Terreiro do Paço fell: the Paço da Ribeira with the royal library and its works of art, the Casa da Índia, the customs house and the Ópera do Tejo, which had opened on 2 April that year.
The royal family was not in the palace that day. King José I and the court moved to Ajuda, to a palace of wood and canvas known as the Real Barraca. On the site of the palace, the rebuilding opened a new square.
How many people died in the 1755 earthquake
Estimates range from 10,000 to 30,000 deaths in Lisbon, a city of about 200,000 people. There is no exact count.
Moreira de Mendonça asked the parish priests and counted just over 5000 dead on the day itself and as many again during November, from injuries and disease. The tsunami alone killed nearly 1000 people in Lisbon. Many families fled to the outskirts and to other towns of the kingdom.
There were no seismographs, so the magnitude is an estimate made from the effects described at the time. The values range from 7.7 to 9. The epicentre was at sea, off south-west Iberia.
How the Baixa Pombalina came about
The government of King José I, with the secretary of state Sebastião José de Carvalho e Melo, the future Marquis of Pombal, had the Baixa cleared and a new town laid out, with straight streets at right angles between the Terreiro do Paço and Rossio.
1755
On 4 December Manuel da Maia, the kingdom’s chief engineer, hands in the first part of a dissertation on rebuilding. The options range from restoring the city as it was to moving it to Belém.
1756
On 12 June the Casa do Risco das Obras Públicas, the public works drawing office, is set up under Captain Eugénio dos Santos, who draws the plan with Carlos Mardel.
1758
A royal charter of 12 May binds the rebuilding to the Casa do Risco plan. The option chosen is to clear the Baixa and lay out new streets, with Rua Augusta down the middle from the Terreiro do Paço to Rossio.
1760
A decree of 5 November names the new streets. Several are named after trades, such as Rua dos Fanqueiros (drapers), Rua dos Correeiros (harness makers), Rua dos Sapateiros (shoemakers) and Rua dos Douradores (gilders).
What the Pombaline cage (gaiola pombalina) is
It is the braced timber frame inside the walls of the buildings of the rebuilt Baixa. It was designed so that a building would sway without collapsing in an earthquake.
Timber inside
The cage sits inside the walls of the upper floors and spreads the forces of the earthquake.
Firewalls
The walls between buildings rise above the roofs, so that fire cannot pass from house to house. The courtyards of the blocks had water wells.
Lower buildings
Building heights were limited to 3 or 4 storeys so that the buildings would better withstand the ground’s motion, and the streets were made wider.
Standard parts
The stone window frames came in two models, one for the main streets and one for the side streets. Producing them in series sped up the building work.
Praça do Comércio in the plan of the Baixa
The square is the plan’s front onto the river. The royal charter of 1758 already fixed its shape, with the king’s statue in the centre and an arch linking it to Rua Augusta.
On the site of the palace, the new square took in the exchange and the customs house, hence the name Praça do Comércio. The statue of King José I was unveiled in 1775. The Rua Augusta Arch, which opens the square onto the Baixa, was completed only in 1875.
Where to see the earthquake today, near the square
On the square itself, the Lisboa Story Centre has a room on the earthquake. 5 minutes’ walk away, the Núcleo Arqueológico da Rua dos Correeiros shows what lies under the Baixa, and uphill on Largo do Carmo the ruins of the Carmo church were left open to the sky.
3 minutes on foot
Lisboa Story Centre
190 mIn the east wing of the square. The route has a section on 1 November 1755, in which the earthquake is recreated in an immersive theatre, and another on Pombal’s plan and the rebuilding.
5 minutes on foot
On Rua dos Correeiros. Layers of Lisbon from the Iron Age to the Pombaline foundations, with a free guided visit.
11 minutes on foot
Carmo ruins
790 mOn Largo do Carmo, uphill. The earthquake damaged the church and the fire destroyed its contents. Rebuilding stopped in 1834 and the naves were left open to the sky as a memorial to the earthquake. Today it is the Museu Arqueológico do Carmo, open Monday to Saturday, with paid entry.
Frequently asked questions
How long did the 1755 Lisbon earthquake last?
According to Moreira de Mendonça, who lived through it in Lisbon, the shaking lasted 6 to 7 minutes, with two short pauses, and began shortly after 09:30 on 1 November 1755. Then came the tsunami, with three large surges, and a fire that burned about a third of the city.
What was the population of Lisbon in 1755?
Nobody knows exactly. Estimates put it at about 200,000 people. Between 10,000 and 30,000 died in the earthquake, the tsunami and the fire, and many families fled to the outskirts and to other towns of the kingdom in the weeks that followed.
How many people died in the 1755 Lisbon earthquake?
In Lisbon, estimates range from 10,000 to 30,000 deaths. Moreira de Mendonça, who lived through the earthquake, counted just over 5000 on the day and as many again during November. The tsunami alone is thought to have killed nearly 1000 people. There were also deaths in Setúbal, the Algarve, Spain and North Africa.
What was the magnitude of the 1755 Lisbon earthquake?
There were no seismographs, so the magnitude is estimated from the effects described at the time. Estimates range from 7.7 to 9, and a University of Lisbon study published in 2020 puts it at 7.7. The epicentre was at sea, off south-west Iberia.
What is the Pombaline cage?
It is the braced timber frame, the gaiola pombalina, inside the walls of the buildings of the rebuilt Baixa, designed so that a building would sway without collapsing in an earthquake. It was part of the rebuilding rules, together with firewalls between buildings and a height limit of 3 or 4 storeys.