The 1722 Algarve earthquake occurred on 27 December 1722. It was felt throughout the Portuguese region of

Algarve The Algarve (, , ; from ) is the southernmost NUTS II region of continental Portugal. It has an area of with 467,495 permanent inhabitants and incorporates 16 municipalities ( ''concelhos'' or ''municípios'' in Portuguese). The region has it ...

and destroyed a large area in southern

Portugal Portugal, officially the Portuguese Republic ( pt, República Portuguesa, links=yes ), is a country whose mainland is located on the Iberian Peninsula of Southwestern Europe, and whose territory also includes the Atlantic archipelagos of ...

generating a local

tsunami A tsunami ( ; from ja, 津波, lit=harbour wave, ) is a series of waves in a water body caused by the displacement of a large volume of water, generally in an ocean or a large lake. Earthquakes, volcanic eruptions and other underwater explo ...

that flooded the shallow areas of

Tavira Tavira () is a Portuguese town and municipality, capital of the ''Costa do Acantilado'', situated in the east of the Algarve on the south coast of Portugal. It is east of Faro and west of Huelva across the river Guadiana into Spain. The Gilão ...

. It is unclear whether its source was located onshore or offshore and, in any case, what was the

tectonic Tectonics (; ) are the processes that control the structure and properties of the Earth's crust and its evolution through time. These include the processes of mountain building, the growth and behavior of the strong, old cores of continents k ...

source responsible for the event. Some scientific research work has concluded that the 27 December 1722 Algarve earthquake and tsunami was probably generated offshore, close to 37°01′N, 7°49′W. The 1722 earthquake was 33 years before the great earthquake of 1755 which remains a major event in Portuguese history, mainly due to its effects on

Lisbon Lisbon (; pt, Lisboa ) is the capital and largest city of Portugal, with an estimated population of 544,851 within its administrative limits in an area of 100.05 km2. Grande Lisboa, Lisbon's urban area extends beyond the city's administr ...

which was wiped out by structural collapse, fire and then the flooding from a tsunami that raced up the

Tagus The Tagus ( ; es, Tajo ; pt, Tejo ; see #Name, below) is the longest river in the Iberian Peninsula. The river rises in the Montes Universales near Teruel, in mid-eastern Spain, flows , generally west with two main south-westward sections ...

River. Most of the documentation of the 1722 Algarve seismic event was sent to Lisbon for archiving and became lost after the fire that followed the 1755 earthquake. But the few surviving written records of the 1722 earthquake describe a destructive series of events affecting several Algarvean localities with earth tremors so strong that they made the bells ring out in Tavira, Faro and

Loulé Loulé () is a city and municipality in the region of Algarve, district of Faro, Portugal. In 2011, the population of the entire municipality was 70,622 inhabitants, in an area of approximately . The municipality has two principal cities: Loulé ...

. In Tavira a caravel moored on the river Gilão was left high and dry before the tsunami hit with the dumbfounded crew able to walk to shore. The magnitude is estimated to have been 7.8 on the Richter scale. The earthquake of 1722 was probably caused by a

diapirism A diapir (; , ) is a type of igneous intrusion in which a more mobile and ductily deformable material is forced into brittle overlying rocks. Depending on the tectonic environment, diapirs can range from idealized mushroom-shaped Rayleigh–T ...

where dense rock from deeper levels under high pressure pierced shallower materials. As a result, buildings in

Albufeira Albufeira () is a city and seat of its own municipality in the district of Faro, in the southernmost Portuguese region of Algarve. The municipality population in 2021 was 44,158, in an area of . The city proper had a population of 28,645 in 2021 ...

, Faro, Lagoa and Loulé were also severely damaged or, in some cases, destroyed. In the 2010s, studies of seismic risk estimated there would be around 12,000 deaths if an earthquake equal to that of 1722 occurred then during peak season, because population density was significantly higher in the coastal areas of Algarve in the early 21st century, when it had already become a popular international travel destination, than in the 18th century, and construction of high-rise buildings built without proper anti-seismic measures were pervasive in the decades preceding such studies.

See also

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