Topographic Disequilibrium in the Columbia River Gorge as a Probe of Magmatic Processes and Volcanic Landscape Evolution
Abstract
The Columbia is the largest river to cross an active volcanic arc. Having maintained its current course through the arc front for roughly 20 Myr the river is both a witness and active driver of volcanic landscape evolution, providing a persistent quasi-static base level for the region, where uplift occurs through tectonics as well as magmatic construction by intrusions and extrusive deposits. Does topography encode signatures of such magmatic uplift? Does it record long-term variations in mantle-driven magma flux? Answering such questions requires deconvolving volcanic influence from overprinting by the Missoula Floods, periodic glaciation, and a complex tectonic deformation field. With this in mind, we have undertaken a systematic analysis of ~1m resolution LIDAR of the entire Columbia gorge and ~10 cm resolution structure from motion (SfM) digital elevation models (DEMs) of cliff faces where the Columbia crosses the arc.
Variations in the distribution, length, and height of steps on hillslopes (cliffs) and in channels (knickpoints) suggest a disequilibrium landscape responding both to local lithology as well as regional baselevel and uplift changes. With many drainage divides pinned by young (< 1 Ma) volcanic edifices one hypothesis is that disequilibrium in the smaller catchments can be used to understand local responses to constructional volcanism, while long wavelength trends impart tectonic signals. To test this we will use spectral techniques to look for long-wavelength structures and compare expected drainage behavior to the current surface, combining SfM-derived DEMs and LIDAR allows us to relate steps to underlying bedrock structures that provide a regionally continuous, mechanically anisotropic substrate for erosion and volcanism. Dated Pleistocene age volcanics and ~15 Ma Columbia River Flood basalt lavas then provides a basis for mapping variations in hillslope form, drainage density, and surface roughness at a range of scales to constrain timescales of incision and uplift associated with constructional volcanism. Although the Columbia Gorge is unique in size, this approach has potential to identify feedbacks between magmatism, tectonics and erosion in all volcanic landscapes.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.V52C..06K
- Keywords:
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- 8408 Volcano/climate interactions;
- VOLCANOLOGY;
- 8414 Eruption mechanisms and flow emplacement;
- VOLCANOLOGY;
- 8424 Hydrothermal systems;
- VOLCANOLOGY;
- 8427 Subaqueous volcanism;
- VOLCANOLOGY