Publications—Open-File Report 2006-1340

Prepared in cooperation with the Departments of Geology and Geography, Portland State University, Portland, Oregon

Digital Outlines and Topography of the Glaciers of the American West

By Andrew G. Fountain, Matthew Hoffman, Keith Jackson, Hassan Basagic, Thomas Nylen, and David Percy

U.S. Geological Survey Open-File Report 2006-1340

The body of the report is available in PDF Format (3,040 KB)

This report is available On-line Only


Alpine glaciers have generally receded during the past century (post-“Little Ice Age”) because of climate warming (Oerlemans and others, 1998; Mann and others, 1999; Dyurgerov and Meier, 2000; Grove, 2001). This general retreat has accelerated since the mid 1970s, when a shift in atmospheric circulation occurred (McCabe and Fountain, 1995; Dyurgerov and Meier, 2000). The loss in glacier cover has had several profound effects. First, the shrinkage of glaciers results in a net increase in stream flow, typically in late summer when water supplies are at the lowest levels (Fountain and Tangborn, 1985). This additional water is important to ecosystems (Hall and Fagre, 2003) and to human water needs (Tangborn, 1980). However, if shrinkage continues, the net contribution to stream flow will diminish, and the effect upon these benefactors will be adverse. Glacier shrinkage is also a significant factor in current sea level rise (Meier, 1984; Dyurgerov and Meier, 2000). Second, many of the glaciers in the West Coast States are located on stratovolcanoes, and continued recession will leave oversteepened river valleys. These valleys, once buttressed by ice are now subject to failure, creating conditions for lahars (Walder and Driedger, 1994; O’Connor and others, 2001). Finally, reduction or loss of glaciers reduce or eliminate glacial activity as an important geomorphic process on landscape evolution and alters erosion rates in high alpine areas (Hallet and others, 1996). Because of the importance of glaciers to studies of climate change, hazards, and landscape modification, glacier inventories have been published for Alaska (Manley, in press), China (, Nepal (Mool and others, 2001), Switzerland (Paul and others, 2002), and the Tyrolian Alps of Austria (Paul, 2002), among other locales.

To provide the necessary data for assessing the magnitude and rate of glacier change in the American West, exclusive of Alaska (fig. 1), we are constructing a geographic information system (GIS) database. The data on glacier location and change will be derived from maps, ground-based photographs, and aerial and satellite images. Our first step, reported here, is the compilation of a glacier inventory of the American West. The inventory is compiled from the 1:100,000 (100K) and 1:24,000 (24K)-scale topographic maps published by the U.S. Geological Survey (USGS) and U.S. Forest Service (USFS). The 24K-scale maps provide the most detailed mapping of perennial snow and ice features. This report informs users of the data about the challenges we faced in compiling the data and discusses its errors and uncertainties.

We rely on the expertise of the original cartographers in distinguishing “permanent snow and ice” from seasonal snow, although we know, through personal experience, of cartographic misjudgments. Whether “permanent” means indefinite or resident for several years is impossible to determine within the scope of this study. We do not discriminate between “glacier,” defined as permanent snow or ice that moves (Paterson, 1994), and stagnant snow and ice features. Therefore, we leave to future users the final determination of seasonal versus permanent snow features and the discrimination between true glaciers and stagnant snow and ice bodies. We believe that future studies of more regional focus and knowledge can most accurately refine our initial inventory. For simplicity we refer to all snow and ice bodies in this report as glaciers, although we recognize that most probably do not strictly meet the requirements; many may be snow patches.




1:24,000-Scale Maps

1:100,000-Scale Maps



1:24,000-Scale Data

1:100,000-Scale Data



References Cited


  1. Map showing distribution of glaciers in the American West
  2. Snow depicted on the 1956 map compared to snow in the 1989 aerial photograph, Eliot Glacier, Mount Hood, OR
  3. Perennial snow/ice patch from the 1946 aerial photograph, the 1958 topographic map, and the 2001 aerial photograph, Icefield Pass, Colorado Front Range
  4. Maps showing errors in the derived vector files compared to the original scanned maps, (A) Sierra Nevada, CA; and (B) Cascades, OR
  5. Maps showing errors in the derived vector files compared to the original scanned maps, (A) North Cascades, WA; and (B) Mount Baker, WA
  6. Maps showing errors in the derived vector files compared to the original scanned map, (A) Sierra Nevada, CA; and (B) Wind River Range, WY
  7. Histogram showing the number of glaciers in the 1:24,000-scale glacier inventory as a function of area
  8. Maps showing Galena Creek Rock Glacier, Absaroka Range, WY, as represented in the 1:100,000-scale and 1:24,000-scale data sets
  9. Histogram showing the number of glaciers in the 1:100,000-scale glacier inventory as a function of area


  1. Lineage and naming conventions for paper and digital products from USGS and USFS
  2. Source of digital data
  3. Errors found in the derived vector data at 1:24,000-scale scanned maps
  4. Earliest photographic date listed for all quadrangles and glaciers
  5. Number of glaciers in the 1:24,000-scale inventory for each area category
  6. Errors found in the derived vector data at the 1:100,000-scale
  7. Glacierized regions in the 1:24,000-scale mapping but not in the 1:100,000-scale mapping
  8. Number of glaciers for each area category

Suggested Citation

Fountain, A.G., Hoffman, Matthew, Jackson, Keith, Basagic, Hassan, Nylen, Thomas, and Percy, David, 2007, Digital outlines and topography of the glaciers of the American West: U.S. Geological Survey Open-File Report 2006–1340, 23 p.

If you have Adobe® Acrobat® or Adobe® Acrobat® Reader® installed on your computer, you may view and print the PDF version of this report. Acrobat Reader, is a free download from Adobe Systems, Inc. Users with disabilities can view information concerning accessibility at .

For further information, contact:

William C. Schwab
Chief Scientist
United States Geological Survey
Woods Hole Science Center
384 Woods Hole Road
Quissett Campus
Woods Hole, MA 02543-1598

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