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The effect of mantle plumes is secondary to that of subducting slabs for modern plate tectonics when considering plate driving forces. However, the impact of plumes on tectonics and planetary surface evolution may nonetheless have been significant. We use numerical mantle convection models in a 3‐D spherical chunk geometry with damage rheology to study some of the dynamics of plume‐slab interactions. Substantiating our earlier 2‐D results, we observe a range of interaction scenarios, and that the plume‐driven subduction terminations we had identified earlier persist in more realistic convective flow. We analyze the dynamics of plume affected subduction, including in terms of their geometry, frequency, and the overall effect of plumes on surface dynamics as a function of the fraction of internal to bottom heating. Some versions of such plume‐slab interplay may be relevant for geologic events, for example, for the inferred ∼183 Ma Karoo large igneous province formation and associated slab disruption. More recent examples may include the impingement of the Afar plume underneath Africa leading to disruption of the Hellenic slab, and the current complex structure imaged for the subduction of the Nazca plate under South America. Our results imply that plumes may play a significant role not just in kick‐starting plate tectonics, but also in major modifications of slab‐driven plate motions, including for the present‐day mantle. Plain Language Summary: Subduction of cold, strong lithospheric slabs is the main plate driving force within mantle convection. However, hot upwellings, mantle plumes, may have a greater role in modulating plate motions and slab trajectories than previously thought. We use 3‐D numerical convection models that account for the weakening of rocks due to the accumulation of deformation to understand the effect that mantle plumes can have on subduction zones. We show that plumes can terminate subduction in a range of circumstances. We also test the effect of the amount of internal heating compared to heat from the core which is the major convective control on the importance of plumes. We discuss cases where these plume‐slab terminations may have occurred on Earth, in the geological past, and for the present day through plate reconstructions and consideration of seismic tomography. Key Points: Mantle plumes can terminate subduction in 3‐D, damage rheology convectionPlumes can modulate subducting slabs and plate tectonic regimesPlume‐slab interactions are plausible contributions to the Karoo‐Gondwana event [ABSTRACT FROM AUTHOR]

Mantle plumes are typically considered secondary features of mantle convection, yet their surface effects over Earth's evolution may have been significant. We use 2‐D convection models to show that mantle plumes can in fact cause the termination of a subduction zone. This extreme case of plume‐slab interaction is found when the slab is readily weakened, for example, by damage‐type rheology, and the subducting slab is young. We posit that this mechanism may be relevant, particularly for the early Earth, and a subdued version of these plume‐slab interactions may remain relevant for modern subduction zones. Such core‐mantle boundary–surface interactions may be behind some of the complexity of tomographically imaged mantle structures, for example, in South America. More generally, plume "talk back" to subduction zones may make plate tectonics more episodic. Plain Language Summary: The main driving force of mantle convection is the subduction of cold, lithospheric slabs. Mantle plumes that rise from the bottom of the mantle are typically not considered as important to plate tectonics, even though they have been suggested to initiate subduction, for example, here, we use 2‐D computer models of mantle convection, with the particular addition of a deformation memory for rocks. We show that mantle plumes can actually stop subduction if certain criteria are met. The weakening behavior of the subducting slab and the overall slab thickness/age are the main criteria for deciding if a plume can stop subduction. We compare our findings to present‐day subduction zones that show indications of possible plume‐slab interactions. One such case is South America, and we consider how this mechanism may play out in a more complicated system. Our findings have implications for early Earth plate tectonics and perhaps present‐day subduction. Key Points: Mantle plumes are capable of terminating subduction in weakened, young subducting slabsPlume‐slab 'talk back' may be seen in tomographic models of present‐day subduction zones, shown here for South AmericaPlume‐slab interactions may explain links between Large Igneous Province eruptions and flat slab episodes for example, for a supercontinental breakup [ABSTRACT FROM AUTHOR]

The Rukwa and North Malawi Rift Segments (RNMRS) both define a major rift‐oblique segment of the East African Rift System and are often regarded as discrete rifts due to the presence of the uplifted Mbozi block between them. Here we investigate the influence of basement fabrics on the coupling and linkage of border faults across an interrift transfer zone between discrete juvenile rift segments. We utilized satellite digital elevation model to investigate the morphological architecture of the rift domains and aeromagnetic data to assess the relationships (plan view) between the rift structures and the prerift basement fabrics. Our results show that the present‐day morphology of the RNMRS is characterized by along‐rift alternation of rift shoulder polarity, characteristic of coupled rift segments. Interpretation of filtered aeromagnetic maps along the boundaries of the RNMRS reveals striking alignment of the rift‐bounding faults with colinear NW‐SE trending preexisting basement fabrics. We find that rift coupling along the NE boundary of the Mbozi transfer zone is accommodated by fault‐assisted magma plumbing, whereas coupling along the SW boundary is accommodated by strike‐slip and oblique‐normal faulting that reactivated the Proterozoic Mughese shear zone, within the collisional boundary between the Tanzania craton and the Bangweulu cratonic block. Further, we show how the configuration of the basement fabrics may influence the formation of rift bifurcation across inter‐rift transfer zones. We suggest that the structural connectivity of the boundary faults along the RNMRS and their alignment with colinear basement fabrics demonstrate the influence of structural inheritance on the amalgamation of approaching rift segments. Plain Language Summary: A few studies, mostly utilizing numerical and analog modeling, have shown that rift basins may nucleate as discrete rift segments that propagate toward one another and merge to form a continuous rift segment. However, there remains a limited understanding of the factors that control how the initial discrete rifts actually link‐up to merge. Rift linkage is expressed by the border fault structure of the interacting rifts, how the border faults link up with one another, and the accompanying deformational structures and processes within the interrift transfer zone. In this study, we investigate the controls of prerift basement fabrics on the border fault structures and linkage of the Rukwa and North Malawi segments of the East African Rift. Our results reveal that the basement fabrics modulate the formation of border fault segments and the merging of these structures across the transfer zone between the Rukwa and North Malawi Rift basins. Key Points: The Rukwa and North Malawi Rift segments exhibit coupled‐rift geomorphologyFault‐guided magmatism and strike/oblique‐slip faulting that reactivated basement fabrics accommodate linkage at interrift transfer zoneBasement fabrics modulate the geometries of the rift border faults and transfer structures, and facilitate linkage between them [ABSTRACT FROM AUTHOR]