The influence of tectonics and climate on basin-fill erosion and incision in the Gulf of Corinth rift,
central Greece, and Rio Grande rift, southwest USA, is examined. Overall, it is suggested that
climate change controls the downstream water:sediment ratio and sediment transport capacity,
via operation of the continuity equation. Tectonics, specifically the rapid growth and propagation
of structures, sets up gradient contrasts and upstream-migrating changes in transport capacity via
operation of the diffusivity equation. A steady-state aggradational mode operated in the southern
Rio Grande rift between ~ 5 and 0.8 Ma, causing preservation of ancestral axial-channel and floodplain
deposits due to relatively slow, long-term active rift subsidence. The onset of major climatic
change around 0.8 Ma resulted in the axial river periodically incising to a total extent of ~ 150 m,
removing about 25% by volume of previously accumulated sediment, despite continued active faulting
and fault-induced subsidence. This climatic mode is interpreted to be a periodic response to
positive downstream gradients in sediment transport rate during glacial and glacial-transition periods,
caused by low-level external sediment sourcing and a dominance of large magnitude spring
snowmelt floods from northern mountain valleys. Tectonic drivers are spectacularly demonstrated
in the Gulf of Corinth, where a new theory of ‘piggy-back’ basin abandonment and regional uplift
is proposed, as formerly active rift-margin faults are progressively dragged above the flat slab of
underriding African lithosphere.