Archeologists at Work
Hard-working Yosemite National Park archeologists hike streamsides and climb steep mountainsides to find archeological sites. Approximately 1,500 sites have been identified, covering only about 10% of the park's large acreage. Thousands of new sites--marked by obsidian artifacts, tree blazes, house pits, privies and foundations--are yet to be discovered and documented within Yosemite. On any given day, archeologists arrive at work to gather tools, which could include compasses, clipboards, GPS devices, trowels, screens or sieves, and digital cameras. Archeologists locate, document, study and manage the archeological resources.
At a glance, here is what archeologists do:
Survey: Archeological survey crew members spread out approximately 20 meters apart and survey the landscape for anything that catches their well-trained eyes. Archeologists document the exact locations of objects, often through GPS to help plot sites. They also take digital pictures of the sites, artifacts and features for the reports. Yosemite archeologists survey the Yosemite backcountry, working with wilderness restoration, firefighters and trail crews to manage their work and avoid potential disturbances to archeological sites.
Monitor: Legislation requires archeologists to be consulted when potential exists for archeological sites to be disturbed through ground disturbances. Construction provides archeologists with an opportunity, if necessary, to sift through displaced soils for artifacts, and archeologists have authority to halt construction to protect resources. American Indian representatives often work alongside archeologists to monitor and retrieve information for their tribes and to educate archeologists on traditional cultural values. Archeological sites on federal property are revisited regularly in order to monitor natural and human-caused threats. Common natural disturbances include erosion, fire, pest infestation, vegetation growth and tree fall. Human-caused disturbances include camping and campfire building, social trailing, off-road vehicle traffic, theft and looting, and vandalism. It's understood that some necessary park operations might threaten archeological sites. These include road and trail building, fire suppression and control, utility construction and operation, waste removal, wilderness restoration, and exotic plant removal. Park archeologists work closely with work crews to avoid these potential impacts.
Excavate: Excavating is a systematic technique that can reveal material remains buried in the layers of soil accumulated through the years. Some sites in Yosemite Valley are six feet deep as a result of thousands of years of habitation and changing environments. A recent excavation in 2008 in the Yosemite Valley recovered approximately 50 stone tools, called pestles, which were used for processing acorn. This represents one of the largest deposits of pestles ever found in the Sierra Nevada.
Research: Research and archiving allows archeologists to examine results, to test new hypotheses or to analyze materials in a different way. Researchers can use objects collected and stored in the Yosemite Museum for this. Obsidian, for example, has different translucency depending on where its original volcanic source is located. And, obsidian from different sources is found in different parts of the park. In the northern locations of the park, obsidian is usually more transparent, indicating that it came from the Bodie Hills area. More opaque obsidian found in the southern part of the park is from the Casa Diablo area. Both of these obsidian sources are located in the Long Valley, east of the Sierra Nevada. To pinpoint the exact source of a piece of obsidian, archeologists use a technique called X-Ray fluorescence, or geochemical sourcing. Another analysis technique is called obsidian hydration dating. The technique measures the microscopic amount of water absorbed by the surface of the obsidian flake, which tells archeologists how long ago that piece was modified. Research can go beyond tangible items to the intangible. Archeologists and anthropologists speak with living descendants of the park’s native people to understand traditional native lifeways. Yosemite National Park maintains a consultative relationship with the seven associated local Indian tribes. Also consulted, at times, are descendents from the cultural groups that are associated with other historic resources of Yosemite.
Did You Know?
Giant sequoias are a fire adapted species. Their bark is fire resistant and fire helps open the sequoia cone and scatter the tiny seeds. Fire also clears forest debris from the mineral soil and provides a nutrient rich seed bed as well as clearing competing species.