Resedimentation of the late Holocene White River ash, Yukon Territory, Canada and Alaska, United States
Dates
Year
2007
Citation
West, Kim D., 2007, Resedimentation of the late Holocene White River ash, Yukon Territory, Canada and Alaska, United States: Carleton University (Canada).
Summary
The White River ash is one of the most distinct and widely dispersed pyroclastic deposits in Yukon-Alaska. It was produced from volcanic eruptions ca. 1887 (north lobe; Lerbekmo et al. 1975) and 1147 years B.P. (east lobe; Clague et al. 1995). The source of the deposit, Mount Churchill, is an ice-covered stratovolcano located 25 km west of the Yukon-Alaska border (61°25'N, 141°70'W). Distal deposits of ash occur as primary airfall over much of Alaska, Yukon, and Northwest Territories. Locally resedimented deposits of ash are common closer to the volcanic source and occur in highly glaciated regions. Distal deposits of White River ash provide important chronostratigraphic control and are used herein to interpret the cultural and environmental [...]
Summary
The White River ash is one of the most distinct and widely dispersed pyroclastic deposits in Yukon-Alaska. It was produced from volcanic eruptions ca. 1887 (north lobe; Lerbekmo et al. 1975) and 1147 years B.P. (east lobe; Clague et al. 1995). The source of the deposit, Mount Churchill, is an ice-covered stratovolcano located 25 km west of the Yukon-Alaska border (61°25'N, 141°70'W). Distal deposits of ash occur as primary airfall over much of Alaska, Yukon, and Northwest Territories. Locally resedimented deposits of ash are common closer to the volcanic source and occur in highly glaciated regions. Distal deposits of White River ash provide important chronostratigraphic control and are used herein to interpret the cultural and environmental impact of ancient large-magnitude eruptions. Sedimentological observations of distal deposits of ash (preserved in fluvially deposited beds) indicates that emplacement of the east lobe of ash occurred during the late fall or early winter. Knowledge of the timing of the east lobe ash is significant to archaeological studies since deposition is associated with the massive migration and expansion of Athapaskan peoples. Locally resedimented deposits of White River ash formed near Mount Churchill when hot volcanic material mixed with snow, ice, and volcanic debris at the summit and descended down surrounding valley glaciers. Large volumes of water and volcaniclastic sediment led to catastrophic thickening of the Russell and Klutlan Glaciers and possibly, temporary lakes from which terraces of ash, up to 20 metres thick, accumulated. Pyroclastic-rich fans formed downstream from resedimented material. Eruptions of Mount Churchill are infrequent events that produce severe volcanic hazards, most notably ashfall and lahars. Future large-scale eruptions would significantly impact tourism, industry, housing and infrastructure and may devastate human and animal populations. Renewed efforts are urgently needed to advance geohazard mitigation in northern Canada and Alaska.
