Posted: Jan 03, 2019 11:06 pm
SkyMutt wrote:
If subduction occurs then significant amounts of crust are recycled into the mantle, correct?
There is an amount of crust recycled, but how that is compared (in the illustration) to the surface crust generated by lithosphere extension?
Ok, I refined the illustration using your remarks to make my point clearer:
- GPS vector field of a tectonic flow.png (84.51 KiB) Viewed 2131 times
So, there is a subduction zone with the consumption of lithosphere at the rate of 30 mm/y.
At the same time, there is extension in the back of the arc that fully balances that consumption of lithosphere.
Indeed, as we move further away from the arc (from position A to E), the velocity decreases which means that there is extension of surface. For example there is an extension of 15 mm/y (30-15=15 mm/y) between positions A and B.
Besides, all positions (including E/F/G/H/I) surrounding the region are immobile relatively to each other, which means that the surface of that rectangular region is constant. So there is subduction, but no gross reduction of the surface of the whole region.
Do you agree?