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Is Slab pull really the dominant force behind tectonic plates movement?
I have been reading about what makes the tectonic plates move. At first, i came across this "passive plate tectonic" theory that mantle convections are the main force behind the movement of tectonic plates. which makes sense to me. However, now it is considered rather obsolete and "Active plate tectonics" theory takes its place which explains the motion of plates in term of gravity. According to it, ridge push and, more dominant one, slab pull derives the plate movement and convection current.
However, i cannot seem to get the grasp of it and there are few lacunas in my mind:
1. There is no slab pull or ridge push if oceanic ridges aren't already formed. Like if there is no divergent boundary in the first place, there will be no raised surface at oceanic ridge and as a result no subduction zones. So, something must have been there to create this divergent boundary and the resulting subduction zones. **if it's not mantle convection then what?** i mean one can use this active theory to explain difference in the movements of different plates or how fast they are moving as compared to mantle convections but i don't know how can it explain the very first plate movement that gave rise to this slab pull and ridge push.
2. If mantle convections really aren't strong enough to make the plates move and slab pull is the one then what is happening at Convergent boundaries of two continental crust?
I would really appreciate any attempt to clear out these confusions.
#science
source
I have been reading about what makes the tectonic plates move. At first, i came across this "passive plate tectonic" theory that mantle convections are the main force behind the movement of tectonic plates. which makes sense to me. However, now it is considered rather obsolete and "Active plate tectonics" theory takes its place which explains the motion of plates in term of gravity. According to it, ridge push and, more dominant one, slab pull derives the plate movement and convection current.
However, i cannot seem to get the grasp of it and there are few lacunas in my mind:
1. There is no slab pull or ridge push if oceanic ridges aren't already formed. Like if there is no divergent boundary in the first place, there will be no raised surface at oceanic ridge and as a result no subduction zones. So, something must have been there to create this divergent boundary and the resulting subduction zones. **if it's not mantle convection then what?** i mean one can use this active theory to explain difference in the movements of different plates or how fast they are moving as compared to mantle convections but i don't know how can it explain the very first plate movement that gave rise to this slab pull and ridge push.
2. If mantle convections really aren't strong enough to make the plates move and slab pull is the one then what is happening at Convergent boundaries of two continental crust?
I would really appreciate any attempt to clear out these confusions.
#science
source
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