Controls on Eolian Landscape Evolution in Fractured Bedrock

Wind abrasion is important for planetary landscape evolution, and wind‐abraded bedrock landscapes contain many landforms that are difficult to interpret. Here we exploit a natural experiment in Chile where topographic shielding by an upwind lava flow yields diverse erosional landforms in a downwind...

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Bibliographic Details
Published in:Geophysical research letters 2019-11, Vol.46 (21), p.12012-12020
Main Authors: Perkins, Jonathan P., Finnegan, Noah J., de Silva, Shanaka L., Willis, Michael J.
Format: Article
Language:English
Subjects:
Abrasion
Atacama
Bedrock
Computational fluid dynamics
Erosion
Erosion rates
Escarpments
Evolution
geomorphology
Landforms
Landscape
Lava
Lava flows
Mountains
Planetary evolution
planetary landscape evolution
Shielding
Steering
Topography
Wind
Wind abrasion
wind erosion
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Summary:Wind abrasion is important for planetary landscape evolution, and wind‐abraded bedrock landscapes contain many landforms that are difficult to interpret. Here we exploit a natural experiment in Chile where topographic shielding by an upwind lava flow yields diverse erosional landforms in a downwind ignimbrite. Using a 3‐D topographic wind model, we find that low velocities in the wake of a lava lobe coincide with a transition from landforms reflecting fracture‐parallel erosion to flow‐parallel erosion. Erosion rates across these landforms vary with shear velocity and abrasion susceptibility of the windward escarpment. We hypothesize that this morphologic threshold is controlled by whether particles can be lofted in suspension and overcome topographic steering imposed by fractured bedrock blocks. Within a phase space set by Rouse and Stokes numbers, our data illustrate that wind‐abraded landforms reflect a competition between the material skeleton of the landscape and the strength of the flow that shapes it. Key Points In wind‐eroded bedrock landscapes, particle abrasion can focus along fracture networks or cross‐cut them, yielding unique landform patterns These erosion patterns emerge from a competition between flow strength, particle inertia, and topographic steering by fractured bedrock Understanding aerodynamic and structural thresholds can help with interpretations of abrasion processes across planetary landscapes
ISSN:0094-8276
1944-8007
DOI:10.1029/2019GL083955