Coastal cliff evolution: Modelling the long-term interplay between marine erosion, initial topography, and uplift in an arid environment

Abstract

Coastal cliff evolution is modulated by several factors, such as uplift, marine erosion, previous topographical conditions, and changes in global sea level. In this study, a numerical model is used to understand the influence of these processes on the evolution of coastal cliffs. This model is based on erosional and tectonic conditions of the Great Coastal Cliff in the Atacama Desert, the tallest and most uninterrupted coastal cliff on Earth. The results show that a faster uplift rate (> 0.3 mm/yr) or an older onset of uplift (3 Myrs) favors the formation of inactive cliffs, whereas active cliffs preferentially form under conditions of a slow uplift (0.2 mm/yr) or a younger uplift onset (1 Myr). Low erosion rates (< 1 m2/yr) also favor the preservation of sequences of staircase marine terraces, separating the seashore from an inactive coastal cliff. In contrast, high erosion rates (≥ 1 m2/yr) inhibit marine terrace formation, keeping the cliff active. The effect of erosion on cliff activity is enhanced or reduced by the slope of the initial topography. Steep coasts (> 5–10°) may hamper cliffs from reaching an inactive state. Thus, this model gives insights on the relative importance of these variables on the development of active and inactive cliffs, especially in an environment such as the Atacama Desert in northern Chile.