Justin Ohlschlager

Masters Candidate

Department of Geology
Portland State University
P.O. Box 751
Portland, OR 97215

The Changing Surface Area and Volume of the Glaciers on the Three Sister Volcanoes, Oregon


Since the maximum of the Little Ice Age, approximately 150 years ago, the glaciers in the Pacific Northwest have been losing both volume and surface area (McDonald, 1995, Jackson and Fountain, 2007, Marcott et al., 2009, Sitts et al., 2010). Anticipated warming air temperatures (IPCC, 2007) suggest that this loss will continue.  Shrinking glaciers have serious ramifications for debris flow hazards and diminished local water resources. Increasing frequency of debris flows will occur due to glacier retreat and no longer buttressing the glacially-carved valley walls on the volcanoes of the Northwest (O’Connor et al., 2001).  Glaciers are major contributes to local alpine runoff in the late-summer months, when the need for water is the greatest during those drier months (Fountain et al., 1998).  While the shrinkage of glaciers removes ice from long-term storage and exports it as runoff, supporting drought-affected stream flow, smaller glaciers have reduced capacity to export the water volume needed to maintain the flows at historic levels.

An assessment of changes in glacier area has not been completed for the Three Sisters Volcanoes, located in Central Oregon (Fig. 1). The most studied glacier in the region, Collier, was the subject of a study investigating the changes in mass from 1910-1994 (McDonald, 1995).  This study is now 17 years old and it looked at only the Collier Glacier.  A total inventory of both the ice area and thickness was completed in 1986, using ground-penetrating radar and surface area-volume estimates (Driedger et al., 1986). 

Oregon Map

Figure 1. Map showing the location of the Three Sisters Volcanoes in the Cascades of Central Oregon (NASA MODIS image, 4.26.2004).

My thesis will estimate the area change of glaciers (Fig. 2) on the Three Sisters based on photographs (ground-based and aerial) and maps.  The earliest photographs date to about 1910 and the most recent were acquired in 2010.  I will also estimate volume change using oblique hand-held photographs.   New advances in digital photogrammetry allow rendering objects in three-dimensions from cameras held at arbitrary angles (EOS, 2004). This offers the tantalizing possibility to derive quantitative surface topography from historic oblique photographs.  Often, historic hand-held photos are the only record of past glacial extents.

location map

Figure 2. Map showing location and extents of the glaciers on the Three Sister volcanoes in Central Oregon. Outlines are from the 1:24,000 USGS topographic maps. The map on the left is North and Middle Sister and the map on the right is South Sister.


Glacial surface areas will be quantified on the Three Sisters Glaciers using a GIS (Geographic Information Systems) whereby historic aerial photographs (Fig. 3) will be georectified using the latest, usable, NAIP orthophotographs (Basagic and Fountain, accepted) and glacier outlines in the photography and imagery will be digitized. Glacier perimeters will be inferred from oblique hand-held photography where necessary to extend or fill gaps in the data record (Sitts et al., 2010).

To estimate the historic surface topography of the glaciers I use PhotoModeler, a software program designed to render three dimensions from a series of overlapping photographs taken from different angles (EOS, 2004).  This software has been used successfully to map the topography of dome growth at Mount Saint Helens during the 2004-2008 period (Major et al. 2009).  From the topographic surfaces rendered in 1910 and in 2010, the difference in surface elevation will be calculated and volume loss estimated.  For control, I will also map the topography of local bedrock and differences there will be used as an estimate of error for the glacial surfaces (Sisson et al., 2011).


Figure 3. Photos of Collier Glacier, situated between North and Middle Sister, in 1910 (left, photo R. Simms) and 1993 (right, photo Weiprecht (USGS)). Significant loss is seen in surface area between the two photos.

Field Work

To provide the most updated information on area and volume change I will acquire new photographs in maximum snow melt, late August/early September.  Photographs taken in 2010, the 100th anniversary of the first photos are taken too early in the summer and seasonal snow obscures part of the landscape.  Therefore, I need to reoccupy the same photograph points, but much later in the season when seasonal snow is at a minimum.


An assessment of volume change is a much more useful metric, compared to area change, in linking glacier change to climate and to effect on alpine stream flow.  Area changes are noisy indicators due to the dynamics of glacier response to mass input and area-volume relations which are not constant over time.  Therefore knowledge of volume changes over the past century will provide a more accurate assessment of glacier change in response to climate.

Perhaps the greatest impact from the project would be the evaluation of a new technique to estimate glacier topography.  Application of Photomodeler to glaciers and for assessing glacier change has not been done previously.  If successful, this technique will be a valuable tool in the analysis of past glacier geometries from photographs from the past, which would give the ability to better utilize data sets (old photos) to there fullest potential.

  • Dr. Andrew Fountain
  • Portland State University Department of Geology
  • The Mazamas, Portland OR
  • Dr. Jim O'Connor, USGS


Basagic, H.J, and Fountain, A.G., Accepted, Twentieth Century Glacier Change in the Sierra Nevada, California, Arctic, Antarctica, and Alpine Research.
Driedger, C.L., and Kennard, P.M., 1986, Glacier Volume Estimation On Cascade Volcanoes: An Analysis And Comparison With Other Methods, Annals of Glaciology, v. 8, p. 59-64.
EOS, Systems Inc. 2004, PhotoModeler User Manual.
Fountain, A.G., and Wader, J.S., 1998, Water Flow Through Temperate Glaciers, Reviews of Geophysics, v. 36, p. 299-328.
Intergovernmental Panel on Climate Change (IPCC), 2007, The AR4 Synthesis Report.
Jackson, K.M., and Fountain A.G., 2007, Spatial and morphological change on Eliot Glacier, Mount Hood, Oregon, USA. Annals of Glaciology, v. 46, p. 222-226.
Major, J.J., Dzurisin, D., Schilling, S.P., and Poland, M.P., 2009, Monitoring lava-dome growth during the 2004-2008 Mount St. Helens, Washington, eruption using oblique terrestrial photography, Earth and Planetary Letters, v. 286, p. 243-254.
Marcott, S.A., Fountain, A.G., O’Connor, J.E., Sniffen, P.J., and Dethier, D.P., 2009, A latest Pleistocene and Holocene glacial history and paleoclimate reconstruction at Three Sisters and Broken Top Volcanoes, Oregon, USA, Quaternary Research, v. 71, p. 181-189.
McDonald, G.D., 1995, Changes in mass of Collier Glacier, Oregon [M.S. thesis]: Oregon State University, 215 p.
O’Connor, J.E., Hardison, J.H.I., and Costa, J.E., 2001, Debris flows from failures of Neoglacial age moraine dams in the Three Sisters and Mount Jefferson Wilderness Area, Oregon, U.S. Geological Survey Professional Paper 1606, 93 p.
Sitts, D.J., Fountain, A.G., and Hoffman, M., 2010, Twentieth Century Glacier Change on Mount Adams, Washington, USA, Northwest Science, v. 84, p. 378-385.
Sisson, T.W., Robinson, J.E., and Swinney, D.D., 2011, Whole-edifice ice volume change A.D. 1970 to 2007/2008 at Mount Rainier, Washington, based on LiDAR surveying, Geology, v. 39, p. 639-642.


Last Updated: July 13, 2011