The results shed new light on processes deep within the Earth that are not only responsible for the formation of mountain ranges, but are also related to earthquakes, volcanism and global cycles of water and resources.
Uunk focused on the transition from oceanic to continental subduction. In subduction, a tectonic plate slides under another plate into the Earth's mantle. When a continental margin is swept along in the process, the dynamics of the system change and mountain formation can begin.
Coherent slices
By carefully dating rocks on Syros, Uunk discovered that parts of a subducting continental margin detach from the descending plate in a remarkably regular manner. These rock packets, originating in the upper hundreds of meters of the continental margin, appear to detach as coherent slices every two to four million years at a depth of about 60 to 70 kilometers in the Earth's mantle.
The results show that these rock slices then end up at different depths within the collision zone, forming a predictable stack in the growing mountain range. This provides a better picture of the processes occurring during the early phases of mountain formation.
Moreover, reconstructions of the pressure and temperature history of the rocks reveal how these deep rocks eventually returned to the Earth's surface. This occurred due to large-scale stretching of the Earth's crust during the formation of the Aegean Sea. This caused rocks that once lay deep in the interior of a mountain range to be raised along large fracture systems and placed side by side at the surface.
Significance findings
Subduction zones are among the most active regions on Earth and are responsible for many earthquakes and volcanic eruptions. A better understanding of the processes occurring in these zones helps scientists more accurately reconstruct and better understand the evolution of such geologic systems.
In addition, subduction processes play an important role in global chemical cycles. Among other things, they influence the distribution of water, raw materials and gases in the atmosphere. The new insights therefore contribute to a better understanding of processes that determine the long-term functioning of the Earth.
With the discovery that rocks are stacked according to recognizable and recurring patterns during the onset of mountain formation, the research makes an important contribution to knowledge about the formation of mountain chains and the evolution of active plate boundaries worldwide.