The city of Lisbon, which is the capital of Portugal,there is a rather distant active tectonic fault, therefore, the occurrence of earthquakes on its territory is extremely unlikely. Despite this, tremors in this area did happen, and one of them even killed hundreds of thousands of people. The local geologist João Duarte studied the seismic history of his hometown for several years in a row and seems to have found the cause of the earthquakes.
One of the worst earthquakes in Lisbonhappened in 1755 - it caused a tsunami that almost destroyed the city and killed 100,000 people. A few centuries later, in 1969, another quake was recorded, which was much weaker and left no victims behind. Geologists still could not explain their causes, but the version of João Duarte sounds quite plausible.
He believes that the cause of the earthquakes lurks ingeological process called serpentinization. It occurs when water is absorbed by rock structures, which leads to the fact that the oceanic lithosphere off the coast of Portugal falls into two. It is believed that the anomaly occurs at the bottom of the Atlantic Ocean along the Iberian Peninsula at a depth of 250 kilometers.
This theory has been tested withcomputer simulation, but the results have not yet been reviewed. If the researchers are right, then this can be considered the first detection of the stratification of the oceanic lithosphere in history. Perhaps, this activity in the future will create a new subduction zone, in which one layer of the Earth's crust will sink under another. As a result, this layering can become the basis for the formation of a new supercontinent.
Recently, scientists managed to uncover the mystery of yet another previously unexplained phenomenon - the formation of a mysterious hole in Antarctica. You can read about it in our material.
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