Michigan’s largest collection of ancient rock carvings by Native Americans is being documented using high-tech lasers and digital models with the goal of preserving the carvings, some fading or disappearing after centuries of weathering or human activity.

Known as the Sanilac Petroglyphs, the rock etchings are the largest known group of ancient carvings in Michigan. Work has been ongoing since 1971 with the state and Saginaw Chippewa Indian Tribe of Michigan. Recently, state agencies, tribes and supporters have been digitally processing 3 billion data points, launching the first of potentially 15-year study.

State agencies including the Department of Transportation, State Historic Preservation Office and Department of Natural Resources, working with the tribe, are using laser-measuring techniques to create digital models of more than 100 carvings in sandstone.

The petroglyphs were discovered in 1881 after the Great Thumb Fire swept through a site now known as Sanilac Petroglyphs Historic State Park. The 240-acre park is considered a sacred site, said William Johnson of the Saginaw Chippewa Tribe Ziibiwing Center of Anishinabe Culture & Lifeways, which has helped document and preserve the drawings.

"The ezhibiigaadek asin (written on stone) conveys the teachings of the Anishinaabek, who occupied the area periodically over the last 8,000 years," Johnson said. "The preservation of the Sanilac Petroglyphs will assist the general public in their understanding of the Anishinabek people, traditional beliefs of the people, preservation, conservation and protection of an irreplaceable historic site and the collaborative efforts of key stakeholders."

The carvings are thought to contain valuable lessons and reflect Anishinabek oral history. Some carvings represent creation and prophesy stories handed down through generations. Others depict daily life and history, such as animal clans and celestial or seasonal events, according to the Ziibiwing Center.

Examples of the carvings include Ebmodaakowet (the Archer) shooting an arrow of knowledge and wisdom into the future. Ebmodaakowet symbolizes the Anishinabek ancestors and their promise to teach the next seven generations, according to the Ziibiwing Center.

Another includes Bimaadiziwin (Life and All Its Meaning): "The never-ending Circle of Life symbol (a spiral) represents our journey and connection to all of creation," according to the center. "Many Anishinabek believe that our earthly walk of life is just the beginning of a long journey."

The Michigan Archaeological Society bought the petroglyphs and surrounding land from private owners in the 1960s. The society donated it to the state of Michigan in 1971 and it is listed on the National Register of Historic Places.

Sanilac Petroglyphs Historic State Park,now managed by the DNR and the Saginaw tribe,is along the Cass River near Cass City in Sanilac County.

Stone tools and pottery found on the petroglyph site on the Cass River floodplain show native groups likely did the carvings in the last 1,400 years, with some possibly created more recently, MDOT said.

After centuries of natural weathering and decades of human activity, some carvings have faded or disappeared, the agency said. Archaeologists have been studying the petroglyphs since the 1920s.

In April, MDOT specialists used terrestrial Light Detection and Ranging, known as LiDAR, along with detailed, close-up photographs to build digital models that will document the site and can be used to track changes in the petroglyphs.

LiDAR instruments collect 3-D information by reflecting laser light off of objects. MDOT typically uses LiDAR to map roads and bridges before construction.

"Part of the reason for collecting this data at this time is to create a digital representation of the carvings in case of further degradation by natural or man-made forces," said Frank Boston of MDOT's Survey Support Unit. "This representation will be available for future generations, regardless of the condition of the actual site. We plan to do a similar data collection in five years so the data can be compared and measured."

Stacy Tchorzynski, an archaeologist at the State Historic Preservation Office who manages the Sanilac Petroglyphs project, said digitally documenting the project is "key to tracking site preservation, supporting tribal and archaeological research, aiding public education projects and leaving a record for future generations."

"The petroglyphs reflect early Native experiences and teachings that continue to matter to people today and will matter to people in the future too," said Tchorzynski. "This significant site commands our greatest respect and care. It is our responsibility to preserve it for future generations."

How to see the carvings

The petroglyphs are located on a prominent outcrop of sandstone that is preserved beneath a pavilion within the Sanilac Petroglyphs Historic State Park at 8251 Germania Road in Cass City. They can be viewed 10 a.m. to 5 p.m. Wednesday through Sunday. A park guide is on hand to provide tours during its open season.

The petroglyphs are closed to visitors during the colder months. The rest of the 240-acre park contains a floodplain forest and a one-mile hiking trail that is open from 8 a.m. to 10 p.m. year-round.

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