The article “Bathymetry of Mariana trench-arc system and formation of the
Challenger Deep as a consequence of weak plate coupling”, by Zohar Gvirtzman, and Robert J. Stern, published by Tectonics describes the study of determining the depths of the Mariana trench-arc system, and how the weak plate coupling results in the formation of Challenger Deep: the deepest known point on earth’s surface. The author’s demonstrate that the Mariana Trench is located at the southwest, and not at the center, because of the width of the plate coupling zone. The authors examine observation methods such as Bathymetry, to know the relation of the Mariana trench with the regional topographic trend, and Seismicity to study the lateral variations along the trench boundary. The plate coupling has been weakening southwards and this has been a matter of investigation. There has been a lot of reorganization at the convergent boundaries near the Challenger Deep segment, and I understand that the formation of Challengers deep is due to the convergent boundaries, and a contracted subducting slab that is formed when the tectonics plates respond to each other.
The weak coupling in the Mariana trench makes it prone to sink and steepen, that result in deepening the trench. National Earthquake Information Center, (NIEC) used the earthquake catalog to find the Wadati-Benioff zone of the Mariana plate boundary is measured to find the existence or regularity of seismic activity in the region. A proposed explanation is required for the reverse topographic trends of the Mariana Trench and Mariana Ridge. The researchers have clarified that the short-wavelength variations in elevation vary in crustal thickness in both ridges and the topographical trends near the plate boundary display a local tectonic process.
It is also understood that the thin plate-coupling zone is uncommon in the Challenger Deep section, and narrow asthenosphere is adjacent to the plate boundary. These factors justify the existence of the deepest point in the southernmost Mariana trench. There is a relation between the deepening of the trench, thinning of the ridge and plate-coupling zone, and vertical and upward spread of asthenosphere. The authors propose that the southward weakening of plate coupling frees the two plates, allows the descending plate to steepen and form a deeper trench and allows the edge of the upper plate to rebound to form a shallower ridge (Gvirtzman, Stern 8).
Mariana is rolling back rapidly due to the hydrodynamic shape of the minor slab, causing an angular moment that overpowers the plate coupling. The authors argue that the lateral forces are not because of the steepening of Mariana, as they believe the roll back is caused by the slab motion driven by simple gravitational sinking due to the hydrodynamic shape. The lateral forces operate on top and bottom of the slab, which resulted in the slab to steep vertically.
This paper contributes to the group presentation, as the information provided on Bathymetry of Mariana trench-arc system and the formation of the Challenger Deep as a consequence of weak plate coupling is an orientation to the measuring methods, and differences that were observed earlier in contrast to the arguments provided by the authors.
Gvirtzman, Zohar. Stern, Robert J. “Bathymetry of Mariana trench-arc system and formation of
the Challenger Deep as a consequence of weak plate coupling”, Tectonics, VOL. 23,
TC2011, 1-15. Web. 10 Feb. 2004.