What makes the 1722 event remarkable is not just its destruction, but its near-total disappearance from the historical record. Most of the documentation of the event had been carefully gathered and sent to Lisbon for archiving. Thirty-three years later, the catastrophic 1755 Lisbon earthquake -- one of the deadliest in European history -- obliterated the capital with structural collapse, fire, and a tsunami that raced up the Tagus River. The archives burned. The 1722 earthquake was effectively consumed by the very disaster it foreshadowed. Only a handful of surviving written records preserve any account of what happened in the Algarve that December day, making it one of the most poorly documented significant seismic events in Portuguese history.

The few records that survived describe a destructive series of events across multiple Algarvean towns. The earthquake generated tremors strong enough to cause structural damage across the region and produced a local tsunami that flooded the shallow coastal areas of Tavira. Whether the source lay onshore or offshore remains scientifically uncertain. Some research has concluded that the earthquake and tsunami were probably generated offshore, but the tectonic source responsible for the event has never been definitively identified. This uncertainty is itself a consequence of the sparse documentation -- the magnitude estimate ranges across more than a full point on the moment magnitude scale, from 6.5 to 7.8, an unusually wide band that reflects how little hard data survived the double calamity of earthquake and archival destruction.

The Algarve sits at the collision boundary between the African and Eurasian tectonic plates, a zone that has generated repeated seismic events over the centuries. The 1722 earthquake was neither the first nor the last to shake this coast, but it occupies a particularly haunting position in the sequence: destructive enough to devastate towns and generate a tsunami, yet invisible enough to be largely forgotten within a generation. The 1755 earthquake overshadowed it so completely that for centuries, discussions of Portuguese seismic history jumped straight from earlier medieval tremors to the Lisbon catastrophe. Only modern scientific research has begun to reconstruct the 1722 event, piecing together the few surviving accounts with geological evidence to understand what the Algarve endured that winter day.

Today, the Algarve coastline shows no obvious scars from 1722. Tavira rebuilt, its whitewashed buildings and tiled rooftops climbing the hillsides above the same River Gilao where that caravel once sat stranded on dry ground. Faro's medieval center was reconstructed. But the geological forces that produced the earthquake remain active beneath the seabed. From the air, the Algarve's barrier islands and shallow lagoons hint at the region's vulnerability -- low-lying landscapes shaped by the same tectonic processes that, three centuries ago, pulled the water from a harbor and sent it rushing back as a wall.