Geomorphologists

Project Description: This page is meant to highlight the research and work undertaken by professional geomorphologists

Recent Publications

• Surface Roughness Dating of Long-Runout Landslides Near Oso, Washington USA, Reveals Persistent Postglacial Hillslope Instability. 2016.

Sean R. LaHusen; Alison R. Duvall; Adam M. Booth; David R. Montgomery

Geology (2016) 44 (2): 111–114.

https://doi.org/10.1130/G37267.1

Summery: This is a graduate student oversight paper. This paper outlines a method of regional prediction of landslide events through field observations, LiDAR maps, and absolute dating techniques. Major landslides in the Washington State area were analyzed using LiDAR data and confirmed with in situ observations and measurements. First and secondary mobilization events were determined scarp steepness. Surface roughness was mapped over a region by measured standard deviation of slope and mapped using GIS software. Each landslide event was radiocarbon dated using debris from the toe. Regression of slope roughness as it relates to slide area is correlated, but variation is high. Error analysis shows issues with definitive dating, as well as secondary mobilization categorized as separate events.

• Dynamic Ridges and Valleys in a Strike-Slip Environment. 2015.

Duvall, A. R., and Tucker, G. E. (2015), J. Geophys. Res. Earth Surf., 120, 2016– 2026, doi:10.1002/2015JF003618.

Summery: Strike-slip faults are long features of tectonic lateral movement and indicative of rotational stress. The main geomorphological characteristic of strike-slip faults are sinstral or dextral lateral offsets of topographic features including hills, streams and rivers. In this paper Duvall develops a model of eroding landscapes where parallel basins capture "beheaded" rivers. Factors in the partial differential equation of the model include: Baselevel lowering, lateral tectonic advection rate, incision rate, and erosion/deposition due to soil creep, with independent variables of channel slope, slope length, drainage area, soil flux, and of course strike slip motion. Results show that in areas of slow lateral offset river incision is efficient along lengthening fault offset, whereas mid speed strike slip movement leaves beheaded streams, reduces drainage basins, and allows for new headwaters to form. The fastest strike slip motions revealed stable headwaters and channel capture. This model should create a a stronger basis for lateral offset calculations along the San Andreas where stream capture normally limits the observability of fast margin offset.

Publications:

• Numerical simulations of glacial-valley longitudinal profile evolution. 2000.

K.R. MacGregor, R.S. Anderson, S.P. Anderson, E.D. Waddington; Geology ; 28 (11): 1031–1034. doi: https://doi.org/10.1130/0091-7613(2000)28<1031:NSOGLP>2.0.CO;2

Summery: As alpine glaciers are the major factor behind cold and/or high elevation valley erosion systems, MacGregor et al construct a numerical model of an alpine glacier and it's tributaries in longitudinal (long axis) form to look at the simulated effects of overdeepening, tributary contribution, and bed erosion. Due to the lack of data on subglacial hydrology, topography, and geology, certain assumptions on erosion due to hydrologic pressure and quarrying are made. Other well defined parameters such as sliding rates, ice mass pressures, ice deformation, mass balance, elevation, and time (tied to oscillating temperatures according to Oxygen-18 records over 400 ka) are used to construct a model simulation that shows a consistent explanation for hanging valleys of tributary glaciers, and overdeepings at their junctions while the oscillation of glacial advance and retreat will erode trunk-ice subglaical steps and overdeepenings at non tributary junctions.