Central American slab tearing controlled by lateral pressure force due to former Farallon subduction

Subduction zones are major convergent boundaries, where the downgoing oceanic plates usually form continuous tabular slabs extending deep into the Earth’s interior. However, many subducting slabs especially those with young ages, exhibit complex geometry, with varying degrees of influence on the overlying continent and surface environment. To better understand the mechanism of such slab deformation, we apply four-dimensional finite element geodynamic models with data assimilation to investigate the evolution of the Cocos subduction in Central America, where a double-slab configuration with complex tearing has recently been observed. We reproduce the subduction history of the Cocos slab since the Eocene. During this period, multiple episodes of tearing occurred within the Cocos slab, starting at 25 Ma. We find that the ancient Farallon slab, subducted during the Mesozoic, enhances the lateral pressure gradient across the slab hinge, promoting eastward mantle flow and tearing of the Cocos slab. The repeated tearing and subduction of the young Cocos plate have shaped the complex slab configuration in the region.