Development of topographic asymmetry: Insights from dated cinder cones in the western United States

Luke A. McGuire, Jon D. Pelletier, Joshua J. Roering

Research output: Contribution to journalArticle

23 Scopus citations

Abstract

Topographic asymmetry, that is, differences in the morphology of landscapes as a function of slope aspect, can be used to infer ecohydrogeomorphic feedback relationships. In this study, we document the dependence of topographic gradients and drainage densities on slope aspect and time/age in four Quaternary cinder cone fields in Arizona, Oregon, and California. Cinder cones are particularly useful as natural experiments in geomorphic evolution because they begin their evolution at a known time in the past (many have been radiometrically dated) and because they often have simple, well-constrained initial morphologies. North-facing portions of cinder cones have steeper topographic gradients and higher mean vegetation cover (i.e., Normalized Difference Vegetation Index, or NDVI, values) under current climatic conditions compared with corresponding south-facing portions of cones within each volcanic field. Drainage density is also higher on north-facing portions of cones in three of the four volcanic fields. These differences in topography were not present initially but developed progressively over time, indicating that the asymmetry is a result of post-eruption geomorphic processes. To test alternative hypotheses for the slope-aspect control of topography, we developed a numerical model for cinder cone evolution and a methodology for estimating local paleovegetation cover as a function of elevation, slope aspect, and time within the Quaternary. The numerical model results demonstrate that rates of colluvial transport were higher on south-facing hillslopes in at least three of the four cinder cones fields. Our paleovegetation analysis suggests that in the two Arizona volcanic fields we studied, higher rates of colluvial transport on south-facing hillslopes were the result of greater time-averaged vegetation cover and hence higher rates of sediment transport by floral bioturbation. Our results illustrate the profound impact that relatively small variations in solar insolation can have on landscapes via feedbacks among hydrology, vegetation cover, and sediment transport. Key Points Microclimatic effects induced by slope aspect influence hillslope formTopographic asymmetry develops on cinder cones throughout the western U.S.Spatial variations in vegetation drive differences in sediment transport rates

Original languageEnglish (US)
Pages (from-to)1725-1750
Number of pages26
JournalJournal of Geophysical Research F: Earth Surface
Volume119
Issue number8
DOIs
StatePublished - Aug 1 2014

Keywords

  • cinder cone
  • hillslope asymmetry
  • landscape evolution
  • numerical model

ASJC Scopus subject areas

  • Geophysics
  • Forestry
  • Oceanography
  • Aquatic Science
  • Ecology
  • Water Science and Technology
  • Soil Science
  • Geochemistry and Petrology
  • Earth-Surface Processes
  • Atmospheric Science
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science
  • Palaeontology

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