Tectonic Shortening Partially Undoes Extension at Mid-Ocean Ridges, Reducing Abyssal Hill Amplitude

المفاهيم الأساسية

Tectonic extension at mid-ocean ridges can be partially reversed by compressive stresses, leading to reverse faulting and reduction of abyssal hill amplitude.

الملخص

The content discusses a process that partially undoes tectonic extension at mid-ocean ridges (MORs), which are sites of divergence between lithospheric plates. The key insights are:

Recent sequences of reverse-faulting earthquakes have been observed about 15 km off-axis at the Mid-Atlantic Ridge and Carlsberg Ridge, indicating tectonic shortening across the ridge flanks.

Mechanical models show that shallow compression of the ridge flanks up to the brittle failure point is a natural consequence of lithosphere unbending away from the axial relief.

Intrusion of magma-filled fractures, manifesting as migrating swarms of extensional seismicity along the ridge axis, can provide the small increment of compressive stress that triggers reverse-faulting earthquakes.

Bathymetric analyses reveal that reverse reactivation of MOR normal faults is a widely occurring process that can reduce the amplitude of abyssal hills (seafloor features covering about two-thirds of the Earth's surface) by as much as 50%, shortly after they form at the ridge axis.

This 'unfaulting' mechanism exerts a first-order influence on the fabric of the global ocean floor and provides a physical explanation for reverse-faulting earthquakes in an extensional environment.

الإحصائيات

Reverse-faulting earthquakes occur about 15 km off-axis at the Mid-Atlantic Ridge and Carlsberg Ridge.
Reverse reactivation of MOR normal faults can reduce the amplitude of abyssal hills by as much as 50%.

اقتباسات

"Tectonic extension at the ridge axis can be partially undone by tectonic shortening across the ridge flanks."
"Intrusion of magma-filled fractures, which manifests as migrating swarms of extensional seismicity along the ridge axis, can provide the small increment of compressive stress that triggers reverse-faulting earthquakes."

الرؤى الأساسية المستخلصة من

Mid-ocean ridge unfaulting revealed by magmatic intrusions - Nature

by Jean... في www.nature.com 04-10-2024

https://www.nature.com/articles/s41586-024-07247-w

استفسارات أعمق

How does the 'unfaulting' mechanism influence the long-term evolution and morphology of the global ocean floor?

The 'unfaulting' mechanism plays a crucial role in shaping the long-term evolution and morphology of the global ocean floor. By reversing the normal faulting process that creates abyssal hills at mid-ocean ridges, this mechanism effectively reduces the amplitude of these features shortly after their formation. As a result, the overall fabric of the ocean floor is significantly altered, with abyssal hills being flattened or reduced in height by up to 50%. This process leads to a more uniform and less rugged ocean floor morphology over time, impacting the distribution of abyssal hills and influencing the overall topography of the seabed on a global scale.

What are the potential implications of this process for our understanding of plate tectonics and the dynamics of mid-ocean ridge systems?

The 'unfaulting' mechanism has significant implications for our understanding of plate tectonics and the dynamics of mid-ocean ridge systems. It challenges the traditional view of mid-ocean ridges as purely extensional environments by demonstrating that tectonic shortening across the ridge flanks can partially undo the extensional processes at the ridge axis. This process highlights the complex interplay between extension and compression in tectonic settings and emphasizes the dynamic nature of mid-ocean ridge systems. By revealing the role of reverse-faulting earthquakes and magma-filled fractures in this process, the 'unfaulting' mechanism provides new insights into the mechanisms driving tectonic activity at mid-ocean ridges and expands our understanding of the forces shaping the Earth's lithosphere.

What other geological or geophysical processes might be influenced by the interplay between tectonic extension and compression at mid-ocean ridges?

The interplay between tectonic extension and compression at mid-ocean ridges can influence a variety of other geological and geophysical processes. One such process is the formation of transform faults and fracture zones, which can be influenced by the stress patterns resulting from the 'unfaulting' mechanism. Additionally, the distribution of volcanic activity along mid-ocean ridges may be affected by the interaction between extensional and compressional forces, leading to variations in magma supply and eruption styles. The development of hydrothermal vent systems, which are often associated with mid-ocean ridges, could also be influenced by the tectonic stress regime resulting from the interplay between extension and compression. Overall, the complex interactions between these tectonic forces at mid-ocean ridges have the potential to impact a wide range of geological and geophysical processes in the oceanic lithosphere.