Earth’s Rotation Variability Triggers Explosive Eruptions in Subduction Zones

Abstract:

The uneven Earth's spinning has been reported to affect geological processes, i.e. tectonism, seismicity and volcanism, on a planetary scale. Here we show that changes of the length of day (LOD) influence eruptive activity at subduction margins. Statistical analysis indicates that eruptions with Volcanic Explosivity Index (VEI)≥3 alternate along opposite subduction zones as a function of whether the LOD increases or decreases. In particular eruptions in volcanic arcs along contractional subduction zones, which are mostly E- or NE-directed, occur when the LOD increases, whereas they are more frequent in backarc extensional settings along W-directed subduction zones when the LOD decreases. We infer that the LOD variability determines a modulation of the horizontal shear stresses acting on the crust-lithosphere. An increase of the horizontal maximum stress in compressive regimes during LOD increment may favour the rupture of the magma feeder system wall-rocks. Similarly, a decrease of the minimum horizontal stress in the back arc extensional settings during LOD lowering generates a larger differential stress, which may enhance failure of the magma confining rocks. This asymmetric behaviour of magmatism contributes to the knowledge of the role of astronomical forces on the dynamics of the solid Earth.