CSDMS 2015 annual meeting poster GeorgieBennett
Landslide and denudational response to transient tectonic uplift in northern California: Lag times and a landslide buzz-saw
Scott Miller
Josh Roering
Corné Kreemer
David Schmidt.
Abstract:
Landsliding dominates the denudational response to uplift in mountainous regions around the world. In settings of steady uplift, it has been suggested that once slopes reach threshold gradients, landslide flux accommodates uplift and limits topographic development. The timescale and process linkages required for landscapes to become threshold slope-dominated, however, involve the consideration of multiple geomorphic lag times. Where channels respond to an increase in uplift rate via knickpoint propagation, we could expect to find a higher rate of landsliding along hillslopes flanking steep, rapidly incising reaches downstream of knickpoints. This is the model we sought to test in the northern Californian Coastal ranges, where the northward migration of the Mendocino Triple Junction causes crustal thickening and rapid uplift at the mouths of the Redwood, Mad and Eel catchments.
We manually mapped ~3000 earthflows and debris slides in the region from high-resolution, multi-temporal aerial photographs in Google Earth. The velocities of active earthflows were estimated by visually tracking features between sequential images. We mapped channel steepness from 10m NED DEMs in Topotoolbox 2 and developed a new tool to automatically define knickpoints along the channel network. We compare these datasets to geodynamically modeled and GPS derived uplift rates and cosmogenic nuclide erosion rates.
Swath-averaged landslide erosion rates match cosmogenic nuclide erosion rates and predicted exhumation rates well both in spatial pattern and magnitude, with a rapid increase proximal to the Mendocino triple junction and a gradual decline to the south. We find that landslides are clustered downstream of knickpoints of an estimated age of ~1.5 Ma. This corresponds to a maximum elevation of 1.5 km (or 1.5 Ma at an uplift rate of 1 mm yr¯¹) observed for the onset of landslide erosion. Landslide erosion limits topographic growth beyond this elevation such that landsliding behaves as a buzz-saw on the landscape. The ongoing southward propagation of the landslide buzz-saw is limited by the rate of knickpoint propagation.
* Please acknowledge the original contributors when you are using this material. If there are any copyright issues, please let us know and we will respond as soon as possible.
