Fig. 2: Tectonic model of magma ascent through the concavely flexed lithosphere.
White arrows indicate the stress fields at the base and surface of the lithosphere. Magmas ascend from a tensional stress field at the base of the lithosphere to a compressional stress field in the upper lithosphere; the least compressive principle stress (σ3) rotates by 90° at middle lithospheric depths. The two black arrows indicate plate motions in the cases of the Japan and Sunda Trenches (A) and the northern Mariana Trench (B) (modified after ref. 2).
