HIGH ALTITUDE ECOSYSTEMS, VOLCANIC ERUPTIONS AND HUMAN LAND USE: A 7,000 YEAR RECORD FROM THE WESTERN ALASKA RANGE

High altitude, periglacial ecosystems, where environments are highly marginal and subsistence resources are sparsely and seasonally distributed, can be fragile in the wake of large-scale disturbances. In Alaska, the deposition of volcanic ash (tephra) is one such disturbance that generally is considered a modern day hazard, especially to air travel. Major volcanic events undoubtedly impacted prehistoric populations Although tephra deposits have been the focus of a wide variety of research in interior Alaska for over 30 years, the impacts to ecosystems and human subsistence and settlement patterns has been under studied.

We present a record of human occupation and tephra deposits in the high altitude (300 to 1,000 masl) periglacial setting of the Western Alaska Range. Shrub tundra vegetation dominates much of the landscape with thin spruce forests and moist tundra in the lower valleys. The initial human occupation extends back to 7,300 cal. years ago, and site types are generally associated with short term, small hunting camps. Artifact density and site extents are relatively low, generally smaller (an average of 21 artifacts per site and 0.15 acres in extent) than those in lower-lying regions in the interior, along major river systems, and in coastal zones. Hunter-gatherer land use patterns at these higher elevations generally consist of short-duration hunting forays by small groups to target seasonally abundant subsistence resources, such as during spring when sheep move to areas of new vegetation or mineral licks, and during the fall mating season. Likewise, access to caribou would have increased during seasonal herd migrations.

Our geological research has defined at least five significant tephra deposits throughout this region that date between 4,000 and 300 cal. years ago. The majority of these were deposited between 4,000 and 2,000 cal. years ago and the volcanic events during this period likely led to ecosystem disturbances and hiatuses of human occupation in this marginal environment. Radiocarbon dating of charcoal and bone from buried soils and archaeological sites above tephra deposits indicates that the ecosystem likely took 900 – 1,200 years to recover after repeated ash falls.