Mysterious Phenomenon is helping the expansion of the Atlantic Ocean each year. Thirty-nine seismometers were implanted on the ocean floor across the mesoatlantic crest as part of the PI-LAB experiment.
An increase in the matter coming from the depths of the Earth’s crust may be driving the continents of North America and South Europe and Africa apart, new research has found.
The plates connected to the Americas are moving away four centimetres a year from Europe and Africa. Between these continents is the Crest of the Middle Atlantic, a place where new plates are formed and a dividing line between the plates that move to the west and those that move to the east. Under this crest, the material rises to replace the leaves’ space as they move away.
Conventional wisdom is that this process is usually driven by alien gravity forces like denser parts of the plates that sink back to Earth. However, the driving force behind the Atlantic plates’ detachment has remained a mystery because dense, sunken leaves do not surround the Atlantic Ocean.
Now a team of seismologists, headed by the University of Southampton, has found evidence of an outcrop in the mantle – the material between the Earth’s crust and its core – from depths of over 600 kilometres below the crest of the Middle Atlantic. It could be pushing the bottom plates, causing the continents to move further apart as a mysterious phenomenon.
The ridges below the mountain ranges are generally believed to originate from much shallower depths, around 60 km. The findings, published in the journal Nature, provide a greater understanding of tectonic plates’ taxonomy that cause many natural disasters worldwide, including earthquakes, tsunamis and volcanic eruptions.
Over two research cruises on RV Langseth and RRV Discovery, the team deployed 39 seismometers at the bottom of the Atlantic as part of the PI-LAB (Passive Image of the Lithosphere Boundary-Asthenosphere) and EURO-LAB (Experiment to Unearth the Boundary Experiment) Oceanic Rheology of the Lithosphere-Asthenosphere). The data provide the first large-scale, high-resolution image of the mantle under the Mid-Atlantic Crest.
This is one of the few experiments of this scale ever carried out in the oceans and allowed the team to imagine variations in the structure of the Earth’s mantle near depths of 410 km and 660 km are associated with abrupt changes in the mineral phases. The observed signal was representative of a deep, slow and unexpected outcrop from the deepest mantle.
The lead author, Matthew Agius, a former postdoctoral fellow at the University of Southampton and currently at the Università Degli Studi Roma Tre, said: “This was a memorable mission that took us a total of 10 weeks at sea, in the middle of the Ocean Atlantic”. The incredible results have shed new light on our understanding of how the Earth’s interior is linked to tectonic plates, with observations not seen before”.
Dr Kate Rychert and Dr Nick Harmon from the University of Southampton and Professor Mike Kendall from the University of Oxford led the experiment. They were the leading scientists on the cruises. The investigation was funded by NERC (Natural Environment Research Council, UK) and ERC (European Research Council).
“There is an increasing distance between North America and Europe, and it is not driven by political or philosophical differences – changes in the mantle cause it,” said Dr Harmon. In addition to helping scientists develop better models and warning systems for natural disasters, tectonic plates also impact sea level and, therefore, affect climate change estimates on geological time scales.
“This was completely unexpected.” It has broad implications for our understanding of Earth’s evolution and habitability”. It also demonstrates how crucial it is to gather new data from the oceans. There is much more to explore,” said Dr Rychert.
Professor Mike Kendall added: “This work is exciting and has long refuted the assumptions that mid-ocean ridges can play a passive role in plate tectonics. He suggests that in places like the Middle Atlantic, the forces at the crest play an important role in separating newly formed plates”.