A secondary flow model for back-arc spreading is developed in this paper that shows some of the characteristics of observed back-arc spreading. Back-arc spreading has formed marginal seas around the west and southwest rim of the Pacific. The episodic spreading and different directions of opening are not completely understood; however, there does appear to be a limited lifetime (< 17 m.y.) and when one episode of spreading ends, there is a lag time (6-10 m.y.) before another adjacent one begins. This suggests that back-arc flow is caused by secondary flow induced by subduction. Simple scaling arguments with physically reasonable values suggest that forced and free convection effects will be nearly equal. A two-dimensional, finite difference model is developed and several numerical experiments lasting 160 m.y. with a varying subduction rate are discussed. These experiments show stress surges lasting 10-20 m.y. and a series of eddies and counter-eddies behind the trench with a spatial scale of 300-400 km. This supports the idea that back-arc spreading is the result of transient eddies induced by the subducting slab.
ASJC Scopus subject areas
- Earth-Surface Processes