Fig. 4

Demonstration that heat flow constraints show that the slab should remain decoupled from the overriding mantle wedge well past the Moho. In all frames, T indicates the location of the trench and VF that of the volcanic front. a Figure redrawn from Furukawa (1993) (faithfully reproduced with the missing horizontal scale). Solid lines: heat flow predicted from his models with a decoupling depth increasing from 40 to 100 km. Gray boxes: averages of the available heat flow data at the time. b Heat flow data for Cascadia with heat predictions from a model below the iMUSH profile over Mount St. Helens and Mount Adams (see text) with the same decoupling depths as in Furukawa (1993) in addition to \(d_c\)=80 km that we use in most of our subduction zone models. Open and filled blue circles as in Fig. 3b but now with the global heat flow database entries projected onto the iMUSH profile. Small grey triangles are the BSR-derived data from Salmi et al. (2017) projected onto the iMUSH profile. c–e 2D temperature plots for the iMUSH cross sections with decoupling depth ranging from 40 km (c), to 70 km (d), and 100 km. The volcanic front is taken to be the location of Mount Adams. While the heat flow data would allow a 100 km decoupling depth the location of the volcanic front clearly does not