Slope diffusion models and digitally-acquired morphometric parameters yield age constraints on cinder cones, examples from the Spencer High Point and Craters of the Moon National Monument, Snake River Plain, Idaho
Abstract
An analytical solution to a diffusion equation for cinder cones and a new digital method for collecting and comparing morphometric data on cinder cones are developed and used to constrain relative KT ages of undated cinder cones from the Spencer High Point (SHP) basalt plateau, southeastern Idaho. We assume that the interior slope of cinder cone craters diffuse at a steady state and that a range of diffusion constants (K=5-15 m^2/ky) derived in other areas of the Intermountain west are applicable in SE Idaho. Previous workers developed diffusion equations that model degradation of the outer flanks of cinder cones over time. The outer flanks of several SHP cones are heavily eroded by landsliding, a non-diffusive process, which invalidates diffusion modeling. However, our observations of the morphology of cinder cones throughout SE Idaho and comparisons with cones in other regions suggest that the interior slopes of cinder cone craters erode diffusively even when the outer flanks of the cones do not. We model and compare KT ages using morphometric measures from both the exterior flanks and the crater interiors; we conclude that the ages based on interior slopes are more valid than those based on exterior slopes. The topographic profiles, used to derive the necessary morphometric parameters (e.g. slope, slope inflection, cone and crater height/width ratios, and crater radius), are generated in a geographic information system (GIS) from readily available 10-m resolution digital elevation models (DEMs) rather than from topographic maps used by previous workers. We analytically solve diffusion equations for cinder cone degradation and compare the consistency of resulting relative KT ages. The one-dimensional equation models how a single topographic profile degrades through time and depends on a diffusion constant K (m^2/ky) that describes the erosion rate. We assume an initial slope of 33° and allow the model to degrade to the slope of the inflection point in the crater interior; this slope is determined by optimizing multiple DEM-derived topographic profiles of the cinder cone. The KT age is based on the amount of time required for the degradation to occur. The models establish relative KT ages between the cones as well as between dated basalt flows of the SHP. These ages will increase understanding of the spatial and temporal migration of stress fields associated with passage of the Yellowstone hotspot, Basin and Range extension, and development of the SHP.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2011
- Bibcode:
- 2011AGUFMEP43C0706B
- Keywords:
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- 3299 MATHEMATICAL GEOPHYSICS / General or miscellaneous