The Lisbon Earthquake of 1755

The 1755 Lisbon earthquake was one of the deadliest natural disasters in history, destroying the capital of the Portuguese Empire and fundamentally altering European intellectual thought.

1. The Event: November 1, 1755

• Time: Approximately 09:40 AM on All Saints' Day.
• Magnitude: Estimated at 8.5–9.0 Mw.
• Epicenter: Atlantic Ocean, approximately 200km southwest of Cape St. Vincent.

2. The Triple Catastrophe

The Earthquake

The shaking lasted between 3 and 6 minutes. In the dense medieval center of Lisbon, 85% of buildings were destroyed, including the Ribeira Palace and its 70,000-volume library.

The Tsunami

Approximately 40 minutes after the quake, a tsunami struck the harbor. Three waves, some estimated at 6 meters (20 ft) high, surged up the Tagus, drowning thousands who had fled to the open waterfront to escape falling buildings.

The Fire

Fires started by cooking lamps and candles in collapsed churches burned for five days. The conflagration destroyed the city's archives and the Casa da India, vaporizing the bureaucratic records of the empire.

3. Casualties and Damage

• Deaths: Estimates range from 30,000 to 60,000 in Lisbon (out of a population of 275,000).
• Economic Loss: Estimated at 32% to 48% of Portugal's GDP.
• Artistic Loss: Irreplaceable works by Rubens, Titian, and Correggio were destroyed.

4. The Marquis of Pombal and Reconstruction

The King’s chief minister, Sebastião José de Carvalho e Melo (later Marquis of Pombal), took command with the order: "Bury the dead and heal the living."

• The Pombaline Cage: A pioneering anti-seismic wooden framework (gaiola pombalina) was mandated for all new buildings.
• The Baixa: The city center was rebuilt on a rational grid system with wide avenues, a landmark in modern urban planning.

5. Philosophical Impact

The disaster occurred at the height of the Enlightenment and challenged the concept of "Optimism" (that we live in the "best of all possible worlds").

• Voltaire: Wrote Poem on the Lisbon Disaster and satirized the event in Candide.
• Rousseau: Argued that the disaster's scale was due to human urban density rather than divine wrath.
• Kant: Wrote three essays on the quake, attempting to find a geological rather than theological explanation—often cited as the birth of Seismology.