Northern Tutchone elders still tell the story of the explosion of
the mountain called Nelruna (Volcano Mountain). While
scientists have not been able to date the oldest of the volcanic
eruptions and lava flows, the youngest of these would appear to be
at least 4,200 years old (Jackson & Stevens, 1992). This is a
recent event geologically but a very old story to have carried
forward in oral tradition.
The Fort Selkirk area features a series of volcanic centres. Nelruna
is the youngest of these although there are the remains of an
older volcano very nearby. Geologists have determined that there
were two or three eruptions that sent lava flowing south from this
mountain. These flows formed into basaltic rock, ranging in
composition among alkaline olivine basalt, olivine nephelinite,
and basanite. This porous, igneous rock forms the basalt cliffs
seen across the river from the townsite. Robert Campbell and his
men hauled chunks of this basalt across the river to build the
chimneys of the original Fort Selkirk.
On at least three occasions, glaciers covered this area to a
depth of over 900 metres. The most recent glaciation in this part
of the Yukon ended some 11,000 years ago and was known as the
McConnell Glaciation. It did not reach quite as far as Fort
Selkirk. During one of the three earlier glaciations Ne Ch’e
Ddhawa, the Selkirk Cinder Cone, erupted. The entire process
took place under the ice. The evidence of this is the unique rock
formation known as basaltic pillows that only form when lava is in
constant contact with water during its emergence and cooling
period. Ne Ch’e Ddhawa lies 7 km upstream from Fort
Selkirk, on the opposite bank.
The lava flows from Nelruna interrupted the flow of the
ancient Yukon River and caused it to change its course. The basalt
flows to the south of Fort Selkirk also formed a dam. Eventually,
the river managed to cut through the basalt and change its course
yet again. Fort Selkirk sits on soils made by the glaciers and
overlain by sands, silts and gravels deposited by the river when
it flowed over this spot.
There has been little prospecting or rockhounding in the Fort
Selkirk area as basalts are not a fruitful source of commercial
minerals and gemstones. Some geodes can be found as well as small
peridots, a gem quality olivine.
Dawson, George. Report on an Exploration in the Yukon
District, Northwest Territories and Adjacent Northern Portion of
British Columbia. Whitehorse: Yukon Historical & Museum
Association, 1987 (reprint of 1888 edition)
Jackson, Lionel. E. Jr. Pleistocene Subglacial Volcanism
Near Fort Selkirk, Yukon Territory. Geological Survey of
Canada, September 1988.
Jackson, Lionel. E. Jr and Brent Ward, et al. The Last
Cordilleran Ice Sheet in Southern Yukon Territory. Géographie
physique et Quatemaire, 1991, Vol 45. No. 3.
Jackson, Lionel. E. Jr and Wayne Stevens. "A recent
eruptive history of Volcano Mountain, Yukon Territory." in
Current Research, Part A; Geological Survey of Canada, Paper