Forces operating within the Earth have been reshaping continents and marine basins over millions of years. What Alfred Wegener published was accepted as an idea in the late 1915 from the 1960s, giving a unified view of our planet. There were two simple reasons that plate tectonic theory took so long to adopt. First, the most important geological forms for its understanding are at the bottom of the oceans. Second, forces controlling the processes operate beneath the seabed and are therefore hidden from view. So much detail about plate tectonics is not yet clear today.
Today, five scientists from the GEOMAR Helmholtz Center for Ocean Research Kiel, Southern University of Science and Technology (Shenzhen, China) and GeoModelling Solutions GmbH (Switzerland) publish a study in the international scientific journal Nature that questions a preconceived notion of plate tectonics. It’s about so-called transformation cracks. “These are major trails in the ridges of the mid-ocean. To date, they have been assigned a tolerant space within a plate tectonics. However, our analyzes show that they are certainly actively involved in shaping the ocean floor, “explained Dr. Ingo Grevemeyer from GEOMAR, lead author of the study.
A look at a global view map of the ocean floor will help to understand the survey. Even at low resolution, several tens of thousands of kilometers of mid-ocean ridges can be identified on these maps. They mark the boundaries of the Earth’s plates. Meanwhile, hot material from the Earth ‘s interior reaches the surface, cools, forming the new ocean floor and pushing the oldest seabed apart. “This is the engine that will keep the plates moving,” explained Dr. Grevemeyer.
However, mid-ocean ridges do not form unbroken lines. They are cut by transverse valleys at almost regular intervals. The individual sections of the ridges begin or end in symmetry at these incisions. “These are the transformational faults. Because the Earth is a sphere, plate movements again cause cracks that produce results on these ridges,” explained Dr. Lars Rüpke from GEOMAR, co-author of the study.
Earthquakes can occur at the metamorphic faults and leave long, so-called fractured zones, on oceanic plates. To date, however, research has assumed that the two plates do not slip past each other at transformation cracks, but that the seabed is not formed or destroyed in the process.
The authors of the current study have now looked at maps of 40 transformation faults in all oceans. “In all instances, we could see that the transformation valleys are much deeper than the adjacent broken zones, which were previously thought of as a simple continuation of the transformation valleys,” says the co-author Dr. Colin Devey from GEOMAR. The team also found signs of widespread magic at the outer corners of the crosses between transformative valleys and mid-ocean ridges.
Using sophisticated numerical models, the team found an explanation for the phenomenon. According to this, the end of the plate next to the transformation defect is deepened in depth, so that peeling occurs. This causes the seabed to expand, creating the deep transformational valleys. Magmatism at the outer corners to the ridges of the middle of the ocean then fills the valleys, until the fractured zones become much thinner. Oceanic crust forming at the corners is therefore the only crust in the ocean formed by two-stage volcanism. It is not yet known what effect this has on the fusion or, for example, circulation of metals in the bark.
Since transformation cracks are a fundamental type of plate boundary and often across active plate boundaries in the oceans, this new discovery is an important addition to plate tectonic theory and thus to our planet’s understanding. . “Really, the view was obvious. But there are simply not enough high-resolution maps of the seabed yet, so no-one has noticed it so far,” he said. Grevemeyer.
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