Theory 39/Volcanic arcs/Ratio lens
Arc Position Is Depth Against Wedge Flow
The claim
The position of an arc is set by the ratio of slab depth to mantle wedge flow rate, so faster wedge flow shifts volcanism away from the trench.
01Mechanism
Melt rises where the wedge is hottest; flow advects that region, and the ratio determines where it surfaces.
02Prediction
Arc position should track the ratio.
03Refutation
Position tracking slab dip alone would remove wedge flow.