Volcanic edifice erosion as a probe of landscape evolution in the Cascades arc

Abstract:

Volcanic provinces exhibit an unusual form of landscape evolution, where topographic construction through magmatism competes with climate and tectonics to determine landscape form. Because rocks are often datable and magmatic construction generates similarly shaped landforms with a known magnitude-frequency distribution, natural erosion experiments play out many times over the lifetime of a volcanic province. Volcanic edifices form through constructional processes, generating quasi-conical landforms that are subsequently degraded through erosion after volcanism ceases. Here, we focus on erosion rates of volcanoes within the U.S. Cascades Arc, where magmatism associated with subduction of the Juan de Fuca plate under the North American plate has culminated in ~3000 volcanic vents of varying shapes and sizes throughout the Quaternary. Because volcanic construction of topography over Myr timescales drives regional precipitation gradients and resulting fluvial and glacial channel network formation, erosion rates derived from current edifice morphology are a defining scale for Cascades landscape evolution.

Using 10m Digital Elevation Models, we analyze the morphology of 2105 cinder cones, domes, shields, and stratovolcanoes with the timing of last known eruptions constrained at the epoch scale. Delimiting edifice topography with a closed-contour algorithm, we distinguish erosional features from volcanic using spectral analysis techniques and morphometric parameters of current topography (e.g., slope, curvature, roughness). We then reconstruct the pre-erosion surfaces to be consistent with average edifice shapes consistent with global trends and individual landform parameters (e.g. edifice basal ellipticity, skew from topographic centroid), from which we estimate Quaternary volcano erosion rates across the arc. Even at the coarse temporal scale of the edifice database, we can distinguish variations in edifice degradation through time as a function of edifice type and position within the arc. Along- and across-arc trends in edifice morphology and erosion are then placed in the context of volcanic construction, modern precipitation, and Quaternary climate.