The Zagros Mountains are nestled in Iran, northern Iraq, and southeastern Turkey, and are the scene of an unfolding geological story deep beneath it. An international team of researchers led by the University of Göttingen released a press statement on the back of publishing the most astonishing results in the journal, Solid Earth, in a paper titled, “The Miocene subsidence pattern of the NW Zagros foreland basin reflects the southeastward propagating tear of the Neotethys slab”. These researchers found that the Neotethys oceanic plate, which once lay between the Arabian and Eurasian continents, is breaking apart, slowly tearing from southeast Turkey to northwest Iran. These findings reveal just how the Earth’s surface, from the creation of mountain ranges such as the Zagros Mountains to the sinking of ocean floors, is shaped by powerful subterranean forces.
A Long-Buried Ocean is Breaking Apart
Source: Solid Journal
The Neotethys Ocean is a prehistoric ocean that existed most of the Mesozoic Era and early-mid Cenozoic Era, tens of millions of years ago. It preceded what we know today as the Indian Ocean, the Mediterranean Sea, and the Eurasian inland marine basins. As the Arabian and Eurasian land masses converged, the ocean slab was forced downward beneath the continents in a process of subduction which eventually resulted in the ocean’s closure and the formation of the Zagros Mountains.
The novelty from Göttingen’s research is that the Neotethys oceanic plate did not just disappear, rather, a portion of it still exists beneath the Earth’s surface and is now tearing apart horizontally, and actively changing the Earth’s surface. This, even though the Neotethys ocean no longer exists.
A Mysterious Depression in the Earth's Surface
One of the motivations behind their research was the puzzle for why the Earth’s surface in the region is sinking faster than anticipated and producing rare crystals in the process. Typically, when mountains are formed from the collision of tectonic plates, the surrounding land is bent downwards under their weight, in a process known as flexure, through which depressions -later filled with sediment forming valleys and plains- are formed.
The land around the Zagros Mountains and the Mesopotamian Basin has sunk by around 3 to 4 kilometers in the last 15 million years. This is deeper than what their calculations said should have happened given the weight of the Zagros Mountains.
The Answer Lies Deep Below
The researchers’ geodynamic models simulated the region's crust and mantle movement and found that this accelerated sinking was probably due to an additional force: the remnants of the oceanic plate beneath the surface dragging down the land from below.
In places such as Turkey, it seems that the oceanic plate has broken off completely. Absent this additional downward pull, this accelerated sinking has not happened. In Iraq and Iran, where the plate remains attached, the region continues to be dragged downward, allowing extra sediment to form within the Mesopotamian Basin.
Implications for Earthquakes, Resources, and More
Renas Koshnaw, the corresponding author for the paper, explained that, “This research contributes to understanding how the Earth’s rigid outer shell functions”. This could enrich our understanding of natural resources such as sedimentary ore deposits and geothermal energy, and help us better understand earthquake risks.
There are then three main consequences that arise from the researchers findings:
Earthquake Risks: This process of the break-up of oceanic plates is likely influencing earthquake activity in the region. Earthquakes can be triggered by large sections of tectonic plates detaching.
Natural Resource Exploration: By improving our understanding of sediment accumulation, geologists will be better placed to explore for natural resources such as fossil fuels and minerals. We already know that the Mesopotamian Basin is rich with oil reserves, and with this new research, we may find new resources.
Geothermal Energy: Finally, our understanding of geothermal energy will be improved, enabling us to better discover this renewable energy source. This is because areas with ongoing tectonic activity typically have higher subterranean temperatures, making them probable sites for geothermal energy extraction.
A Window into Earth's Hidden Forces
This fascinating research is a window into the Earth’s hidden forces, reminding us that the Earth’s surface is constantly, though imperceptibly changing. It is easy to look at mountains and valleys and see symbols of stability and timelessness, and yet, seen through the prism of millions of years, they are moving. The Earth is in motion, not only in terms of the Solar System, but in terms of its surface and the deep-below. Through a heightened understanding of these processes, we are better able to predict geological changes, discover energy sources and assess the potential impacts of this movement on humanity.
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