Lava flows and legends—Quaternary earthquakes, volcanism, and catastrophic outburst floods in central Yukon Territory, Canada
by
Lionel E. Jackson, Jr.
Geological Survey of Canada and Department of Earth Sciences, Simon Fraser University, Canada

The tectonically quiescent Yukon Plateau (YP) in central Yukon Territory, Canada is bordered to the west by the North America plate margin (NAPM) which is characterised by subduction and strike-slip seismicity and subduction-related volcanism. Neogene uplift within NAPM is estimated to be in the 3 m/ka range. By contrast, YP has averaged only about 0.01 m/ka over that interval. Over the past 2.7 Ma, tectonic stability of YP has been punctuated by locally extensive outpourings of alkaline basaltic lavas. In the Fort Selkirk area, these have dammed the Yukon River, creating short-lived but very extensive lakes ca. 1.37 and 0.311 Ma. Lava dams were up to 100 m high. Breaching of the lava dams caused outburst floods that left boulder beds immediately down-stream. Flood discharge was sufficient to erode and transport blocks several metres in length more than 70 km downstream from lava dam breaches. During the 10-20 ka tenure of humans in YP, early to middle Holocene volcanism occurred in the Volcano Mountain area and the region was buried by two thick tephra falls from eruptions in NAPM (Wrangell Mountains) during the past 2 ka. Earthquakes, centered on sources along NAPM and within the fold and thrust belt along the eastern margin of the northern Cordillera, have also repeatedly shaken YP. Such events are recognized in the oral tradition of Northern Tutchone-speaking aboriginal people in the area.

Date received: February 20, 2002

Copyright © 2002 by the author(s). The author(s) of this document and the organizers of the conference have granted their consent to include this abstract in Atlas Conferences Inc. Document # caiq-10.