Lithospheric slab breakoff can occur in various styles including a horizontal ‘tearing’, where an initial weakness develops into tearing and laterally propagates along the slab. Slab tearing has been invoked to explain changes in plate kinematics in the Western Mediterranean and the tectonic uplift that led to the Messinian Salinity Crisis. However, this process remains debated regarding its surface signature and the physical parameters controlling its initiation and dynamics. Here, we use 3D thermo-mechanical modelling to investigate geodynamic parameters affecting the slab-tearing initiation and its lateral propagation, and to quantify the corresponding surface vertical motions. We find that an oblique convergence introduces an asymmetry that favors the initiation of one-sided slab tearing. The tectonic configuration of the overriding plate has little effect on the trench migration rate, and slab tearing can results purely from the negative buoyancy of the subducted slab. This force and the slab retreat it causes are enough to generate an arcuate plan-view shape to the orogen. The slab-tear propagation rate varies from 37-67 cm/yr. During propagation, the slab tearing depth increases along the subducting slab, with a shallow initial tear (80-150 km) and a deeper tear (170-200 km) on the opposite end. The time needed for the slab to detach completely is geologically fast (<2 Myr). The slab tearing can cause a prominent surface uplift of 0.5-1.5 km throughout the forearc region with an uplift rate of 0.23-2.16 mm/yr, which is consistent with the situation during the first stage of the Messinian Salinity Crisis.

Lithospheric slab tearing, the process by which a subducted lithospheric plate is torn apart and sinks into the Earth’s mantle, has been proposed as a cause for significant surface vertical motions. However, little is known about the mechanisms that help initiate slab tearing and the consequential topographic changes. This study aims to explore this process by means of 3D thermo-mechanical modelling. We use the Gibraltar Arc region (Betics Cordillera) as a reference scenario of continental collision where such tearing-uplift interaction has been proposed. Our results suggest that the obliquity of the continental passive margin (relative to the trench axis) is a major influence on the initiation of slab tearing because it promotes a laterally diachronous continental collision, which leads to earlier tearing inception in one end of the slab. As a result of this, the model results predict an east-to-west slab tearing (tearing velocity 37.6–67.6 cm/yr with the lower-mantle viscosity of up to 1e+22 Pa·s). While the fast slab tearing (<2 Myr over 600 km wide slab) and the lack of arcuate slab in our models limit a direct comparison with the Western Mediterranean, this approach provides a new insight into the link between slab tearing in the mantle and surface uplift. Our models yield uplift rates of 0.23–2.16 mm/yr in response to slab tearing. This range is compatible with the uplift rate needed to achieve an equilibrium between seaway-uplift and seaway-erosion, which could have led to the closure of marine gateways during the onset of the Messinian Salinity Crisis.