Repeat Photography Project

Science Center Objects

Repeat photography provides objective visual evidence of landscape change. USGS scientists created approximately sixty repeat photography pairs that document glacier change in Glacier National Park. These photograph pairs are available as a collection hosted by the USGS Photographic Library and are publicly available for download.  Modern (1997 to 2019) photographs were taken from precisely the same location as historic (1887 to 1943) photographs, enabling direct comparison of the landscape then and now. The photographs document glacier change and illustrate the impact of climate warming on the glaciers of Glacier National Park.

USGS Repeat Photography Collection

Collection Highlights (some beautiful examples)

Full Collection – two platforms to browse and download images:

USGS Photographic Library

USGS ScienceBase

The Glacier RePhoto Project  - view and contribute to glacier re-photo efforts in the American West

Repeat photo of Grinnell Glacier

Boulder Glacier in 1910 (Elrod photo, GNP Archives) and in 2007 (Fagre/Pederson photo, USGS).  Matching the intersection of the peaks in the background helps the repeat photographer locate the photo point. (USGS. Public domain.)


USGS Repeat Photography Project

Map of glaciers re-photographed by USGS in Glacier National Park

Map of glaciers re-photographed by USGS in Glacier National Park. Red dots indicate that the associated glacier has at least one repeat photo pair in the Repeat Photography Collection. (Credit: L. McKeon, USGS Northern Rocky Mountain Science Center. Public domain.)

In 1997 the USGS began re-photographing historic glacier images to document changes to the park’s namesake features.   An abundance of historic glacier imagery, captured by early twentieth century photographers interested in tourism promotion and scientific study, provides the foundation for repeat photography in Glacier National Park (GNP).  USGS staff and volunteers generated repeat photograph pairs by taking copies of historic photos into the field, finding the precise location where that photograph was taken, and then repeating the same photo, years apart. Historic and modern era photo pairs were then displayed side by side in Park hotels, museums, and as shown on the GNP Glacier Repeat Photos website, for viewers to compare and assess landscape change. 

Repeat photo pairs were immediately popular with the media and the public as visual representations of the impact of climate change on glaciers.  Efforts to capture, archive, and provide publicly accessible images became known as the USGS Repeat Photography Project, which generated a collection of over sixty repeat photo pairs.  The images have inspired artistic collaborations and museum displays, the creation of teaching materials, and a variety of public uses of the imagery which include quilting, modern dance performance, and the inclusion on a gold-plated disc orbiting the Earth with a selection of  images that represent humanity. 

Capturing Repeat Photographs of Glaciers

 Historic glacier images for the USGS Repeat Photography Project were selected from collections at Glacier National Park Archives, the University of Montana Archives Photography Collections and the USGS Photographic Library.  Historic photographs were selected for repeat photography based on the image containing clearly exposed bare ice and glacier margins that are not obscured by seasonal snow.   Google Earth was used to obtain approximate photo coordinates to aid relocation of the photo point in the field. Locating the precise field position of the original photo then involved triangulation of landscape features and moving up and down the hillside to replicate exact elevation.

USGS employee taking repeat photo of glaciers

USGS employee captures a repeat photo of Grinnell and Salamander Glaciers from the summit of Mt. Gould in Glacier National Park. (Public domain.)

Field excursions to capture repeat historic images were scheduled in late summer to document the glacier free of seasonal snow at the margins.  Several challenges were inherent to the late summer restriction because this window of opportunity frequently coincided with inclement weather, forest fire smoke, lengthening shadows, and early winter snowfall.  For example, weeks of forest fire smoke prevented re-photography during late August and early September for at least four field seasons between 1997-2019. Only a few glaciers have trails that offer easy access, therefore, visiting most of the park’s glaciers requires multi-day backcountry travel.  As a result, the most accessible glacier, Grinnell Glacier, has the most repeat photo pairs (n=23) in the Glaciers of Glacier National Park Repeat Photography Collection.     

Record of a Changing Landscape

Since 1997, USGS scientists repeated and established re-photo sites for over twenty different glaciers in GNP.  Glacier recession is the most striking change documented by these photo pairs. Yet close inspection of the photographs in this collection reveal other landscape changes in addition to retreating glaciers. Establishment of vegetation along newly melted glacier margins and changes in forest composition are evident in multiple photo pairs (e.g. Jackson, Sperry, and Piegan Glacier images). The collection also documents some forms of human use in the park and serves as a visual record of a dynamic landscape.

The Repeat Photography Project was one chapter of  USGS glacier research. This visual documentation of glacier change in Glacier National Park paved the way for ongoing studies of glacier mass balance, glacier response to climate, and regional assessments of glacier mass change. This photograph collection complements the long term records and research insight generated from the USGS Benchmark Glacier Research project.

Repeat photo of Grinnell Glacier (1910, 2016)

Grinnell Glacier in 1910 and 2016. Retreat resulted in glacier fragmentation, so the 2016 scene shows both Grinnell Glacier, hugging the base of the cliff, and The Salamander Glacier, perched above, along the right edge of the photograph. (Credit: 1910-Elrod photo, U of M Collection and 2016-McKeon photo, USGS. Public domain.)


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