• Human and ecological responses to the Northern White River Ash eruption

      Smith, Holly A.; Reuther, Joshua; Bigelow, Nancy; Clark, Jamie (2020-05)
      The White River Ash northern lobe (WRAn) volcanic eruption deposited a blanket of tephra (volcanic ash) along the Yukon-Alaska border ~1625 cal BP (calibrated years before present). Currently, there has been limited investigation into the effect of this natural disaster on the environment and local hunter-gatherer populations. This research seeks to analyze and explore the potential ecological and cultural responses to the WRAn event. To address this question, paired archaeological and palynological studies bracketing the WRAn were conducted. Excavations at the Forty Mile/Ch'ëdä Dëk Territorial Historic Site in the Yukon (LcVn-2) revealed a multicomponent site including cultural deposits dating to approximately 1500 and 2000 years ago, with a band of WRAn ash separating them. The focus of the project was to identify similarities and differences in artifactual and faunal assemblages and feature types between cultural occupations pre- and post-tephra deposition that could indicate variations in site use, hunting practices, and tool manufacture. A decadal-scale pollen analysis spanning ~80 years before and after the WRAn tephra fall was conducted on a lake core collected near Eagle, Alaska, to explore the potential environmental impacts of the tephra deposition on the landscape. Results from this project suggest that the WRAn eruption did not create a prolonged negative environmental or cultural impact. At the study location, which experienced at least ~1 cm of tephra deposition, there is a prompt reoccupation of the Forty Mile Site, with multiple subsequent occupations, displaying a resilient population that was able to adapt to the fluctuating environmental surroundings. Similarly, the pollen displays a period of ~5 years of reduced influx and productivity, followed by spikes of abundance before returning to pre-eruptive comparable levels ~35 years after the WRAn. In this thesis, I argue that no hiatus in cultural occupation occurs following the WRAn tephra deposition and the archaeological assemblage displays characteristics in accordance with general cultural transitions occurring in southwestern Yukon and interior Alaskan archaeology.
    • Modeling volcanic ash and sulfur dioxide with the Weather Research Forecasting with Chemistry (WRF-Chem) model

      Egan, Sean D.; Cahill, Catherine; Stuefer, Martin; Webley, Peter; Lopez, Taryn; Simpson, William (2019-12)
      The Weather Research Forecasting with Chemistry (WRF-Chem) model is capable of modeling volcanic emissions of ash, sulfur dioxide and water vapor. Here, it is applied to eruptions from three volcanoes: the 2008 eruption of Kasatochi Volcano in Alaska, the 2010 eruption of Eyjafjallajökull in Iceland and the 2019 eruption of Raikoke in the Kurile Islands. WRF-Chem's ability to model volcanic emissions dispersion is validated through comparison of model output to remote sensing, in situ and field measurements. A sensitivity of the model to modeled plume height is discussed. This work also modifies the base WRF-Chem code in three ways and studies the effects of these modifications. First, volcanic ash aggregation parameterizations are added covering three modes of particle collisions through Brownian motion, differential settling and shear. Second, water vapor emissions from volcanic eruptions are added and coupled to the new aggregation scheme. The effects of these changes are assessed and found to produce volcanic ash concentrations in agreement with in situ measurements of plume concentrations and field measurements of tephra fallout. Third, the model is adapted to include multiple model initializations such that each is perturbed by selecting between two volcanic ash particle sizes and five initial plume heights. This modified WRF-Chem is nested in an application program interface that enables a new, automated, near real-time capability. This capability is assessed and the feasibility of its use as an augmenting tool to current operational VATD models is commented upon.