Carol A. Stein-
Subduction Zones & Hydrothermal Circulation Research

It has been commonly assumed that heat flow in the incoming plate at subduction zones is lower than expected for crust of that age due to increased hydrothermal circulation from flexure and faulting.



Left: Figure from Masson [1991] showing a subduction zone region. Right: Sketch showing expected heat flow variations near subduction zones after Uyeda [1977]. Heat flow is expected to decrease on the incoming plate approaching the trench due to flexure (starting about 300 km from the trench) and faulting in the outer trench region (starting about 50-75 km from the trench). FB=Forearc Basin. SC=Subduction Complex.

I tested this suggestion by examining heat flow measurements made near all trenches and compared these values to the average measured heat flow for the same age crust. I found that there is no change in heat flow approaching the trench near subduction zones due to flexing and faulting of the crust as previously commonly assumed. However, on average, heat flow in the overriding plate is ~60% of that in the incoming plate [Stein, 2003].

Heat flow fraction (measured/observed global average heat flow for that age) with distance from the trench axis. Within the faulted outer trench slope, heat flow fraction does not decrease compared to the average values.

Hence this analysis suggests that the incoming crust at subduction zones has the same thermal structure as expected for its age compared to lithosphere far from plate boundaries. Sparse measurements on incoming crust with relatively thin sedimentary cover have slightly lower heat flow, suggesting more water circulation.


Masson, D. G., Fault patterns at outer trench walls, Mar. Geophys. Res., 13, 219-225, 1991.

Stein, C. A., Heat flow and flexure at subduction zones, Geophys. Res. Lett., 30, No. 23, 2197 doi 10.1029/2003GL018478, (05 December) 2003. For pdf click here

Uyeda, S., Some basic problems in the trench-arc-back arc system, in Island Arcs, Deep-sea Trenches and Back-arc Basins, Maurice Ewing Ser., 1, eds., Talwani, M and Pitman, W. C. III, 1-14, Am. Geophys. Un., Washington, D.C., 1977.

This material is based upon work supported by the National Science Foundation under Grant No. 0001941. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.