Preliminary evaluation of the fire-related debris flows on Storm King Mountain, Glenwood Springs, Colorado
No abstract available.
Colorado↗
Geology topics
William P. Rogers
Publications and source records attributed to William P. Rogers.
Modelling the bathymetry of the Antarctic continental shelf
Continental shelves are typically covered by relatively shallow waters (<200 m) which deepen gradually from the coast to the shelf edge. The continental shelf around Antarctica is deeper than normal (400-700m) and is characterized in many areas by a nearshore trough (up to 1 km deep) that gradually shallows toward the shelf edge. We examine the cause for the unusual shelf bathymetry of Antarctica by 2-D numerical models that simulate the bathymetry along seismic line ODP-119 in Prydz Bay. Line ODP-119 was chosen because it is tied to to 5 ODP boreholes, and because the margin underwent little recent tectonic activity or changes in the glacial drainage pattern. The numerical models incorporate several factors that are likely to influence the bathymetry, such as the load of the ice cap, the isostatic response of the lithosphere, thermal and tectnoic subsidence of the margin, sea level changes, and the patterns of erosion and sedimentation across the margin. The models show that the observed bathymetry can be produced almost entirely by the sum of the outer-shelf sediment loading and inner-shelf unloading and by the load of the slope sediments. A simple statistical mdoel demonstrates that this distribution pattern of erosion and deposition can be generated by multiple cycles of ice sheet advances across the shelf, whereby in each cycle a thin (a few tens of meters) uniform layer of sediments is eroded from under the ice sheet and is redeposited seaward of the grounding line.
Conference Paper↗
Morphology and age of fault scarps in the Rio Grande Rift, south-central Colorado
Fault scarps in the Rio Grande rift of Colorado provide most of the evidence of paleoseismicity in the state, and are thus a major focus of assessments of earthquake hazards. Critical components of such assessments are the ages of past faulting events; age control is scarce and generally coarse for the Rio Grande rift in Colorado. Ages estimated from fault-scarp morphology are thus valuable, partly because they are directly related to the fault eVents, and partly for want of alternative methods. The processes responsible for scarp degradation are poorly understood and the many variables that affect the rates and relative importance of those processes limits the precision and accuracy of age estimates derived from scarp morphology. Both analytical and empirical methods are available for relating scarp degradation processes to scarp morphology and age. Diffusion-equation models that have been derived for scarp degradation are useful for their predictive value and for the insight they provide about the degradation processes. However, because of the limitations mentioned above and because of the multiple-event nature of the scarps in the Rio Grande rift, the simpler empirical approach involving the relation between scarp angle and the logarithm of scarp height is used here. The scarp-morphology data from the Rio Grande rift suggest that the youngest movements on all of the scarps examined occurred less than 15,000 years ago, with the exception of two scarps that are formed on lithologically dissimilar deposits. This age estimate is consistent with the observation that all of the scarps occur at least in part on deposits of Pinedale age. The scarp-morphology data suggest that some of the scarps are closer to 5,000 years than to 15,000 years in age; several of these scarps occur on deposits of early Holocene age and are associated with early Holocene radiocarbon dates. One scarp occurs on deposits with radiocarbon dates of only a few thousand years, although the morphology of this scarp is unusual for its age. Three scarps have morphologies that suggest that they may represent fault events younger than 5,000 years old. Although no corroboration is available, these scarps may represent some of the youngest fault movements in Colorado.
Colorado↗