9.5 Mechanisms Of Plate Motion

9.5 Mechanisms for Plate Movement

It has been oft repeated in this text and elsewhere that convection of the drapery is critical to plate tectonics, and while this is almost certainly so, in that location is withal some debate about the bodily forces that brand the plates movement. Ane side in the argument holds that the plates are only moved by the traction caused by drape convection. The other side holds that traction plays only a small role and that two other forces, ridge-push and slab-pull, are more important (Figure 10.28). Some argue that the real answer lies somewhere in between.

Effigy 9.28 Models for plate motion mechanisms [SE]

Kearey and Vine (1996) have listed some compelling arguments in favour of the ridge-push/slab-pull model, as follows: (a) plates that are attached to subducting slabs (e.g., Pacific, Australian, and Nazca Plates) move the fastest, and plates that are non (e.k., North American, South American, Eurasian, and African Plates) motility significantly slower; (b) in society for the traction model to utilise, the drape would have to be moving most five times faster than the plates are moving (considering the coupling between the partially liquid asthenosphere and the plates is not potent), and such loftier rates of convection are non supported by geophysical models; and (c) although large plates have potential for much college convection traction, plate velocity is not related to plate area.

In the ridge-push button/slab-pull model, which is the one that has been adopted by almost geologists working on plate-tectonic issues, the lithosphere is the upper surface of the convection cells, as is illustrated in Figure 9.29.

Figure 9.29 The ridge-button/slab-pull model for plate motion, in which the lithosphere is the upper surface of the convective systems. [SE]

Although ridge-push/slab-pull is the favoured mechanism for plate motion, it's important not to underestimate the role of pall convection. Without convection, there would be no ridges to push from because upward convection brings hot buoyant rock to surface. Furthermore, many plates, including our own Northward American Plate, move along nicely — albeit slowly — without any slab-pull happening.