The 1755 Lisbon earthquake, also known as the Great Lisbon Earthquake, occurred in the Kingdom of Portugal on Saturday, 1 November 1755, the holiday of All Saints’ Day, at around 09:40 local time.
Seismologists today estimate the Lisbon earthquake had a magnitude in the range 8.5–9.0on the moment magnitude scale, with its epicentre in the Atlantic Ocean about 200 km (120 mi) west-southwest of Cape St. Vincent. Tsunamis as tall as 20 metres (66 ft) swept the coast of North Africa, and struck Martinique and Barbados across the Atlantic. A three-metre (ten-foot) tsunami hit the Irish coast. Estimates place the death toll in Lisbon alone between 10,000 and 100,000 people, making it one of the deadliest earthquakes in history.
Deep and yawning chasms were carved out along the Clare/Galway coastline at Killomoran, Caherglissane and Kinvara acting as testament of the great Lisbon earthquake in 1755.
A castle at Coranroe on the north coast of Clare was also destroyed.
It is also alleged that Aughinish Island in County Clare was created as a direct result of the Tsunami having previously been part of the Clare mainland. Uniquely in Ireland, this present day Island is separated from its own County by sea, but is joined to another County by road, in the sense that a road to the island was built across a causeway from County Galway by the British for access to a Martello Tower constructed in fear of Napoleonic invasion (1804-1810).
Above is an image of the present day Pier at New Quay, Co. Clare with Aughinish Island to the right which was allegedly severed from the Clare mainland following the 1755 Tsunami.
The Tsunami is also said to have entered Galway Bay and allegedly caused damage to the Spanish Arch(es) in Galway.