This research, led by João Duarte, involved mapping the seafloor off the coast of Iberia and has led to the discovery of a 186 mile long subduction zone in the Atlantic Ocean, 120 miles from Portugal. Put simply, the Earth’s crust consists of a number of tectonic plates, which move across the surface of the mantle, driven by convection currents deep within the Earth. When two plates collide, the denser plate subducts underneath the other, which is less dense, forming a subduction zone.
The newly discovered subduction zone is not yet fully developed and is instead in ‘an embryonic’ stage, in the words of Duarte. The crack that is forming in the ocean floor will lead to the Eurasian splitting into two parts, one continental and one oceanic. The denser Oceanic section will then subduct underneath the Continental plate, leading to the Atlantic Ocean shrinking as North America and Europe are pulled together. Eventually, the two continents will be joined together and the resulting collision will lead to a new mountain range forming and a supercontinent, similar to Pangea, could potentially develop. This process will not be a fast one and the first significant changes will only begin to manifest themselves after roughly 20 million years. In approximately 220 million years the Atlantic Ocean should have closed up completely.
Scientists have been mapping the Atlantic Ocean seabed near Portugal for many years now for signs of potential tectonic activity and this discovery marks the first significant evidence that a subduction zone is indeed forming. The area has experienced relatively regular earthquakes, the most destructive of which was the 1755 earthquake, which had an estimated magnitude between 8.5 and 9. The primary impact of the earthquake and the series of tsunamis that were created by the seismic energy combined to destroy an ill-prepared Lisbon, killing 60000 people. It is predicted that earthquakes will become more common and increase in magnitude in the area around the subduction zone as it develops.
The discovery of this newly forming subduction zone, could contribute significantly to the field of plate tectonics, as further monitoring will allow for a greater understanding of how subduction zones initially form and the way in which supercontinents develop as oceans disappear. Duarte has suggested a possible cause behind this being that the subduction cycles of the African and Eurasian plates, which were previously being driven into one another, have subsided, resulting in the mountain ranges stretching from west to east across Europe and into Asia. There is existing evidence for this idea, as when the plates in the Pacific began to decrease in movement, two subduction zones, similar to one seen of the coast of Portugal, formed, one in the North Atlantic and the other near Antarctica.
Despite the fact we will never see the impacts of this subduction zone, as is inevitable with most geology and plate tectonics, it is fascinating to see how the series of supercontinents that have formed over time were made and how they broke apart, with this discovery in the Atlantic Ocean shedding new light on the field.
Contributed by James Axton