In 1969, a massive earthquake off the coast of Portugal triggered a tsunami that killed over a dozen people. An even larger earthquake had occurred in the same area some 200 years earlier destroying the city of Lisbon and killing around 100,000 people. Two earthquakes in the same spot over a span of 200 years is generally not a cause for alarm but these tremors have specifically puzzled the seismologists as they originated in relative flatbeds of the ocean, away from any known faults or cracks in the Earth’s crust where tectonic plates slide past each other, releasing enormous amounts of energy with earthquakes.
A recent theory proposed that a tectonic plate is splitting into two layers with the top sheet peeling off the bottom one may be causing these rumbles under the seemingly quiet area. A group of scientists reported this possibility in April at the European Geosciences Union General Assembly held in Vienna stating that this unusual phenomenon has never been observed before. According to their abstract, this peeling may be forming a new subduction zone i.e. an area in which one tectonic plate is rammed beneath another. This isn’t the first time this hypothesis has been proposed but this group of scientists is the first to provide supporting data on it.
According to National Geographic, this peeling into layers is possibly driven by a water-absorbing layer in the middle of the tectonic plate. This central layer might have undergone the geological process of serpentinization in which water seeps in through cracks causing a layer to transform into soft green minerals. National Geographic reported that this transformed layer might be causing sufficient weakness in the plate for the bottom layer to peel away from the top layer. Such peeling could cause deep fractures that may trigger a tiny subduction zone, in turn, causing catastrophic earthquakes and possible shrinking of the Atlantic Ocean.
The scientific team tested their proposition with two-dimensional models. Their preliminary results show that such activity is indeed possible but is yet to be proven. This research is yet to be published in a peer-reviewed journal.