Ice Patch Archeology in RMNP

"We must learn, and we are gradually learning, how to write history with the help of archeology."

-Michael Rostovtzeff 

Ice patches are increasingly recognized as reserves for archeological resources across the world.

Ice patches offer important resources for mountain-dwelling animals like respite from summer heat and insects. Because of this, indigenous peoples also utilized these sites to hunt game animals. Ice patches that are relatively isolated, at lower elevations, and located along gentle, more accessible terrain tend to capture and preserve more archeological materials.

An ice patch in Rocky Mountain National Park.

Photo Courtesy of Jason LaBelle

Unlike glacial ice that flows and deforms over time, ice patches are relatively stable bodies. This stability helps preserve artifacts, even perishable materials, for hundreds or thousands of years. Once an artifact melts out of the ice patch, however, organic components begin to rapidly decompose.

As climate change increases the rate of ice patch recession, it is important to identify and document potential artifacts released from ice patches and to record the current extent of ice patches in the park. From 2015-2018, a group of researchers from Colorado State University (CSU) visited ice patches across Rocky Mountain National Park (RMNP) to document natural and cultural remains melting out of these sites. The team also collected baseline data on ice patch location, size, and the types and composition of artifacts associated with each location. Over the next several decades of anticipated ice patch melt, baseline data will offer a reference with which to compare future ice patch resources.

A bison skull discovered from an ice patch in Rocky Mountain National Park.

NPS Photo

During their four seasons of field work, the research team surveyed 30 ice patches and documented 329 items, including 86 animal specimens, 242 wood specimens, and 4 cultural items. Animal remains discovered included skulls, bones, and teeth from a variety of game species. These included deer, bighorn sheep, elk, and bison. Wood specimens from one site helped identify a new group of ice trees. Previous work identified preserved spruce trees estimated to be ~4,200 years old. Potential cultural items identified included several modified wooden items and one large quartzite flake, possibly a cutting tool that may have been sourced from quartzite exposed at lower elevations east of the park.

A stone tool discovered from an ice patch in Rocky Mountain National Park.

Photo Courtesy of Jason LaBelle

While RMNP strives to preserve natural and cultural artifacts in place, a selection of documented items from this study were approved for further laboratory analysis and carbon dating. Carbon dating not only provides a relative age of the artifact; it also provides a “minimum age” for the ice patch it was released from. Radiocarbon dates for collected items ranged from modern times to 2000+ years old (big horn sheep bone). Most specimens, however, are estimated to be ~600 years old, suggesting most ice patches surveyed as part of this research were formed during that last Little Ice Age, a period of regional cooling, that occurred in this area.

This research contributes to a growing body of knowledge in RMNP and a larger mosaic of similar studies being conducted around the world.