207-10 Reconstructing the Lithospheric Response to Plume-Driven Uplift of the Northwestern Ethiopian Plateau

Session: Honoring the Late Professor Mohamed Abdelsalam: Outstanding Researcher, Generous Colleague, Legendary Mentor, and Ambassador for the Geosciences In Africa

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Abstract:

The northwestern Ethiopian Plateau, juxtaposed with the Ethiopian Rift to the east, has been uplifted to a mean elevation of approximately 2.5 km, attributed to the combined effects of the rising Afar mantle plume, rift flank uplift associated with the East African Rift System, and isostatic adjustment following sediment removal by the Blue Nile and its tributaries. Morphotectonic studies indicate that this uplift occurred in three distinct phases—ca. 29–10 Ma, 10–6 Ma, and 6 Ma to present—resulting in ~2 km of total elevation gains since the early Oligocene. Of this, only ~0.3 km is attributed to isostatic response to sediment unloading, leaving ~1.7 km of residual uplift unexplained by surface processes alone. To investigate the underlying lithospheric structure and the sources of this residual uplift, we applied the Moho topography modeling algorithm developed by Gómez-Ortiz and Agarwal (2005), extending it into an ensemble modeling framework to simulate variations in crustal thickness beneath the Plateau. Steady topographic growth due to a buoyant mantle was modeled by applying time-dependent mantle buoyancy forces, assuming viscoelastic properties for both the lithosphere and mantle. Results from 5,000 simulations of Moho topography reveal pronounced crustal heterogeneity, including Moho shallowing beneath major drainage systems, suggesting that active sub-aerial processes contribute to thermal uplift. A steady-state uplift model driven by a buoyant mantle plume indicates that sustained mantle upwelling over the past 30 million years could plausibly account for the Plateau’s progressive growth. These findings significantly contribute to our ongoing research aimed at modeling how plume-related uplift modifies the thermal, density, compositional, and seismic structure of the lithosphere, refining scientific understanding of the dynamic processes responsible for surface uplift in mantle-influenced terrains.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

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