Lisbon, the capital of Portugal, is rather far active faults, therefore, on its territory the occurrence of earthquakes is extremely unlikely. Despite this, the tremors in this area still occurred, and one of them even claimed the lives of hundreds of thousands of people. Local geologist joão Duarte for several years studied the seismic history of his native town and seems to have found the cause of earthquakes.
One of the worst earthquake in Lisbon occurred in 1755 — it caused a tsunami that almost destroyed the city and killed 100 000 people. A few centuries later, in 1969, there was another quake, which was much weaker and did not leave behind victims. Geologists still could not explain their causes, but the version of joão Duarte sounds quite plausible.
He believes that the cause of earthquakes lies in the geological process called serpentinization. It occurs when the water absorption of rock structures, which leads to the fact that the oceanic lithosphere off the coast of Portugal falls apart in 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 was tested using computer simulation, but the results have not yet been reviewed. If the researchers are right, this can be considered as the first discovery of stratification of the oceanic lithosphere in history. Perhaps this activity in the future journey to a new zone of subductionin which one layer of the earth’s crust will sink beneath another. The result of this layering can become the basis for the formation of a new supercontinent.
Recently, scientists have managed to reveal the secret of another previously unexplained phenomena — education mysterious hole in Antarctica. You can read about this in our material.