Preliminary Interpretation of Pre-2014 Landslide 

Deposits in the Vicinity of Oso, Washington

By Ralph A. Haugerud

Open-File Report 2014–1065

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

SALLY JEWELL, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia: 2014

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Suggested citation:

Haugerud, R.A., 2014, Preliminary interpretation of pre-2014 landslide deposits in the vicinity of Oso, 

Washington: U.S. Geological Survey Open-File Report 2014–1065, 4 p., 

http://dx.doi.org/10.3133/ofr20141065. 

ISSN 2331-1258 (online)

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Preliminary Interpretation of Pre-2014 Landslide 

Deposits in the Vicinity of Oso, Washington

By Ralph A. Haugerud

High-resolution topographic surveys allow fairly precise mapping of landslide deposits 

and their relative ages. Relative ages are determined by cross-cutting relations and the amount of 

smoothing—more smoothed slide deposits are older—of these deposits. The Tulalip Tribes, in 

partnership with the Puget Sound Lidar Consortium, acquired a high-resolution lidar (light 

detection and ranging) survey of the North Fork Stillaguamish River valley in 2013. This report 

presents a preliminary interpretation of the topography of this area using the lidar data at a scale 

of 1:24,000. 

Figure 1 is an elevation model derived from 1:24,000-scale contours on published U.S. 

Geological Survey (USGS) topographic maps. Resolution is low and artifacts resulting from 

interpolation of the contours and projection to a raster image are evident. The red cross-hatched 

area marks the approximate extent of deposits from the March 22, 2014, landslide. A red line 

with tick marks the approximate position of the March 22 headscarp. Both features were mapped 

from news photographs and their locations are not precise. 

Figure 2 is an elevation model calculated from the 2013 lidar survey. Colored areas show 

older landslide deposits, distinguished by their relative age: A, youngest to D, oldest. Relative 

ages are estimated by cross-cutting relations and the amount of smoothing. Each deposit was 

derived from the adjacent uphill arcuate scarp. Relative ages are valid for adjoining landslide 

deposits, but do not necessarily indicate simultaneous formation. For example, all deposits of age 

B were not created during the same time period. All landslides are younger than the retreat of the 

Puget lobe of the Cordilleran ice sheet, which in this area probably occurred about 14,000 years 

ago. Landslides classed as age A include the 2006 Steelhead Haven landslide to the northeast, 

and the Skaglund Hill landslide to the southwest, which was active in 2006 and 2011. The red 

cross-hatched area marks the approximate extent of deposits from the March 22, 2014, landslide. 

A red line with tick marks the approximate position of the March 22 headscarp. Both features 

were mapped from news photographs. 

These interpretations are preliminary and are based entirely on topography. Where 

younger events (for example, fluvial erosion or deposition) have eroded or buried landslide 

deposits, their distinctive morphology will not be evident. The actual extent of landslide deposits 

is probably greater than shown. In a very few locations, morphology may not be diagnostic. 

Mapping is only one of several elements in a landslide-hazard assessment. Stratigraphic 

and chronologic studies are necessary to establish landslide frequencies. Mechanics of past and 

potential future landslides need to be analyzed to better understand the potential for future failure 

and the potential for rapid movement. Forecasts of climate change and river meandering may be 

essential.
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The accompanying geodatabase includes four vector feature classes

• OldLandslideArcs: Arcs delimiting landslide deposits and the limits of the interpreted area

• OldLandslidePolys: Polygons built from OldLandslideArcs and attributed with relative age

• NewLandslidePoly: Approximate extent of the March 22, 2014 landslide deposit

• NewLandslideScarp: Approximate position of headscarp of the March 22, 2014 landslide 

Also included in the geodatabase are raster shaded-relief images

• Tulalip2013_nw: Calculated from 2013 lidar topography (available from the Puget Sound 

Lidar Consortium website under 2013 Tulalip Project) 

• NASA2003_nw: Calculated from 2003 lidar topography (available from the Puget Sound 

Lidar Consortium website under Data from Other Agencies) 

• NED13_nw: Calculated from digital topography derived from 1:24,000-scale contours 

(available from the National Map, 1/3 arc-second National Elevation Dataset) 
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Figure 1. Shaded-relief image of elevation model derived from 1:24,000-scale contours on published U.S. Geological Survey (USGS) topographic 

maps. The red cross-hatched area marks the approximate extent of deposits from the March 22, 2014, landslide.
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Figure 2. Shaded-relief image calculated from the 2013 lidar survey. Colored areas show older landslide deposits, distinguished by their relative 

age: A, youngest to D, oldest. The red cross-hatched area marks the approximate extent of deposits from the March 22, 2014, landslide.