How strong was the 1755 Lisbon earthquake?

Modern estimates put it around magnitude 8.5 to 9.0, followed by a tsunami and city-wide fires. Tens of thousands died.

Why is it important beyond the destruction?

The systematic parish survey afterwards is considered the origin of seismology, and the disaster reshaped European philosophical debate about optimism and providence.

Is the time reliable?

Contemporary accounts place the first shock at roughly 9:40 in the morning local time, recorded here in UTC.

November 1, 1755

1755-11-01 09:40 UTC

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The Lisbon earthquake

A massive quake, then a tsunami, then fire destroys Lisbon on All Saints' Day and shakes European philosophy.

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What happened in this minute

The first shock struck around 9:40 in the morning, while churches were full for All Saints' Day. Survivors who fled to the waterfront were met by a tsunami, and fires burned for days in what remained.

The Marquis of Pombal's response, surveying damage with a questionnaire sent to every parish, is often called the first scientific study of an earthquake and the beginning of seismology.

It also broke something intellectually. Voltaire and Rousseau argued publicly over how a benevolent order could permit it, and optimism as a philosophical position never fully recovered.

Questions and answers

How strong was the 1755 Lisbon earthquake?: Modern estimates put it around magnitude 8.5 to 9.0, followed by a tsunami and city-wide fires. Tens of thousands died.
Why is it important beyond the destruction?: The systematic parish survey afterwards is considered the origin of seismology, and the disaster reshaped European philosophical debate about optimism and providence.
Is the time reliable?: Contemporary accounts place the first shock at roughly 9:40 in the morning local time, recorded here in UTC.