HELMVILLE — Rubber galoshes rising to his knees, archaeologist Steve Platt shaves through a layer of concrete-colored ash at the bottom of a trench. The trench has filled with water from last night’s rain, but the ash has been here for 6,850 years, deposited by a cataclysmic eruption 900 miles away.
The eruption of Mount Mazama in the Oregon Cascades was the largest volcanic event to hit North America in at least 10,000 years. The ash rained down for days, burying a prehistoric camp that archaeologists are now working to uncover in western Montana. The tools and trappings of that ancient band of people were capped by the workings of geology and hidden until now.
Located between Helmville and Drummond in the belly of a sage-covered valley, the Paleo Indian campsite marks one of the oldest prehistoric finds uncovered in western Montana. Every turn of the shovel offers a fascinating view of early man’s exsistance, the geology that shaped this land, and mankind’s ability to adapt to its changing environment.
A group of University of Montana students first discovered the camp in the 1960s. Funded by the Montana Department of Transportation, the dig was reconvened last summer. It is, Platt notes, the final step before the reconstruction of Highway 271 buries portions of the site. Historical Research Associates Inc. of Missoula is conducting much of the work, which ends this week.
Platt, an archaeologist with MDT, stuffs the trowel back into his pocket. He’s been out here most of the summer and the group’s findings — namely the stone chips and fragments of bone — get him excited.
“I think we’re on an old travel route,” he says, kicking mud from his boots. “This was undoubtedly a base camp for Paleo Indians. They would have spent more time here than they would at a hunting camp. You have to think about resources.”
Platt points west toward the slope of a nearby mountain. There — about a half-mile in the distance — archaeologists have found a chert quarry. The black rock, along with obsidian and dacite, were used to make stone tools including the knives, spear tips and hide scrapers found throughout the site. During that time, the game was abundant and the water fresh. Nearly everything they needed to survive the summer months was right here.
On a day not unlike this one 6,850 years ago, Mazama blasted 3,000 feet of mountaintop, opening a caldera five miles wide and one mile deep (today’s Crater Lake in Oregon). The sky turned dark and ash swirled down in a terrible blizzard of grit over the Pacific Northwest.
The ominous cloud drifted as far east as Billings and as far south as Reno, Nev. For a band of ancient people, the event was likely frightening. How it altered their lives, nobody really knows. But given the impacts the 1980 eruption of Mount St. Helens had on our modern civilization, Mazama — whose eruption was more than 40 times larger — would have disrupted life for hundreds of years.
“The ash is like ground-up glass,” Platt said. “It would have worn out the teeth of the animals that grazed here pretty fast. It’s perfectly possible that people may have left this site for a few hundred years. It would have been tough going and dusty.”
The ash in this particular pit is nearly a foot deep. Platt believes this spot of ground was once lower than the rest. In a trench 100 yards away, the ash layer is thinner, measuring just a few inches thick.
“I’m not going to say we’re standing on Pompeii because we’re not,” Platt said. “But because these artifacts were capped by an act of geology, we know much more than we otherwise would have.”
The Mazama eruption may have done more than darken the sky and create a storm of lung-choking ash across the Pacific Northwest. Bill Eckerle, a geoarchaeologist based in Salt Lake City who has a long history of digging in Montana, believes the Mazama eruption changed the climate. It’s his job to determine if the artifacts found here were moved by time, or if they are resting where humans discarded them thousands of years ago.
When dust-sized material falls out of the atmosphere, it buries the artifacts gently, he explains. But when a river spills its banks, the action is more intense and can move objects from their original location. It doesn’t seem like it would matter much, as the artifacts have been preserved either way. But for a sleuth like Eckerle, the difference is enormous.
“We’re trying to figure out what kind of plants and animals lived in the area, what resources were available to the people who stayed here,” he said. “The Mazama ash is real nice. It has set a wonderful marker.”
Standing near a small square trench, his face shaded from the sun, Eckerle points across the sage-covered valley and explains how it once contained cottonwoods, gooseberries and cottontails.
After the eruption, however, the wetlands turned dry. The once-flat valley filled with sediment that washed the mountains during torrential thunderstorms. That changed the contour of the land. Over time, the accumulation of sediment forced the stream into a narrow channel. In Eckerle’s words, it became “entrenched.” The dry vegetation, once captive to the upper slopes, began to spread.
“What we’ve found indicates that this area had more moisture,” he said. “It was more meadow-like, and I think the valley was wider and flatter in here. After the Mazama ash fell, it looks like we got more material coming off the slopes. A wedge of sediment worked into the valley. A drier climate prevailed.”
Despite the geologic activity, the artifacts haven’t moved far from their original location. The deepest deposits have been kept from human eyes for 9,000 years, dating back to a time when glacial ice was still retreating from eastern Canada.
The bow and arrow hadn’t been invented yet, and wouldn’t be for more than 7,000 years. Paleo Indians hunted with atlatals and spears. Antelope, bison, beaver and bighorn sheep likely were abundant.
Archaeologists have already found ancient bone fragments from bison and beaver at the site. Platt pulls a chunk of ungulate bone from the wall of one trench. Bones like this were often crushed and boiled. The fat — melted from the marrow — was mixed with berries and used to cure meat in a product Platt referred to as pemmican.
“If you’re job was to go out and kill game for your family, you’d get pretty good at making tools,” Platt said. “It’s not a super-lengthy process. It only takes a skilled worker 15 to 20 minutes to complete each tool.”
Aside from cured meat, Paleo Indians turned to biscuit root — or wild carrot — along with cammas that still grows in abundance not far from here. Future generations made “cous cakes” by grinding roots into a powder and mixing it with water before baking it in an underground oven.
Stones cracked from the heat of fire lie scattered throughout the campsite. Platt spots small flakes of obsidian no larger than a penny — remnants of tool making. He picks them up from the dirt, explaining how a prehistoric oven might lay buried beneath our feet.
Steve Aaberg, a paleobotonist, has surveyed various sites around Montana to determine what Paleo Indians ate during their travels. Plant fiber alone won’t survive the test of time unless it’s been charred. So he is digging around fire pits and ovens looking for evidence of past diets. He’s already found a few charred seeds.
“We hope to find charred plant remains so we can get evidence of root processing,” he said. “To find those materials preserved, you have to get lucky.”
It helps knowing the flora that’s already out there; things like biscuit root, bitterroot, cammas and other edible plants. Most of them were here 9,000 years ago. Recipes may have been passed down through generations, though archaeologists have found little scientific or cultural evidence linking Paleo Indians with today’s Native Americans.
While the techniques in tool making changed among prehistoric man, so have modern dating techniques within scientific circles. Aaberg may not need the charred plant itself to form a hypothesis. A new form of DNA testing, or protein analysis, can read proteins off buried tools, even after thousands of years have passed.
“The plant and animal proteins will stick to the tools,” he said. “We’re hoping that as we submit some of these tools for testing, we’ll pick up traces of plant proteins to help us learn what they ate.”
The valley sweeps north toward the Bob Marshal Wilderness and south to the Garnett Mountains. The sage grows in clumps and the Blackfoot River runs quietly behind a distant knoll.
Such are the workings of time. The people who traveled through this mountain corridor proved hearty and adaptable. Their tools evolved and their styles changed, though archaeologists don’t entirely know why.
It’s in that bottom layer of soil, just below the ash, where archaeologists find the first indication of human presence in what would become Montana. People occupied North America beginning 11,500 years ago, though Platt admits that the dates are often disputed.
Back then, the Pleistocene era was coming to a close, yet glaciers still covered large portions of North America. Mammoth, bison, giant sloth and camels roamed the open tundra. Montana’s earliest people likely lived in small bands comprised of extended families. When traveling, they followed the major river valleys.
When the ice age came to a close, temperatures warmed. The environment changed. The emerging grasslands and expanded forests became less fertile. By about 9,000 years ago, the time Platt’s band of Paleo Indians camped here, most of the larger mammals had disappeared from the state.
Yet the chips of animal bone and stone tools buried here extend from the deepest layer of soil up to the surface. Some relics are as recent as the 19th century when European explorers, like Granville Stuart, arrived on the scene. Stuart, an early Montana cattle baron, traded with various tribes including the Nez Perce, Flathead, Kootenai and Kalispell.
“We have a layer cake of stratification with evidence of human occupation spread throughout it,” Pratt said. “I even found a button shell off an old cowboy’s shirt. We’re acting as detectives, piecing together what people did.”