A millions-of years-old fissure in the tectonic plate off Cape St Vincent in the Algarve has just been discovered and thought to have revealed the mystery of the Great Lisbon Earthquake of 1755.
That earthquake devastated Portugal’s capital city and surrounding area as well as all along the Algarve coast and beyond. It had a magnitude of 7.7 in its epicentre in the Atlantic Ocean 200 kilometres (120 miles) west-southwest of Cape St Vincent near Sagres, which is about 290 km (180 miles) southwest of Lisbon.
Saturday 1st November, normally celebrated in Portugal as All Saints Day, has also been described as Portugal’s “Darkest Day”. Between 20,000 and 30,000 people died in the capital and thousands more in the Algarve, Spain and Morocco.
The 1755 catastrophe, Europe’s worst earthquake ever, was accompanied by wildfires and massive tsunamis. Although unprecedented, it was the third major earthquake in the region, lesser ones being in 1332 and 1531. Scientists were again left questioning a 7.8 or 7.9 level earthquake in Portugal in 1969.
The study published this week suggests that the dense, hot mantle below the Earth’s surface causes a process called ‘declamation,’ causing severe stress. The result of the study could resemble the Pacific Ocean’s “ring of fire” that fuels about 430,000 earthquakes each year, and about 68% of all volcanic eruptions since 1960.
1 comment:
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