Iskut-Unuk River cones Lava Fork Lavas
Start: 360 yBP ± 60 Years [1]
Event Type: Effusive
Description: From Stasiuk and Russell (1990): "The Lava Fork lavas are the youngest volcanic rocks of the Iskut River region and may represent the youngest volcanic eruptions in Canada (Elliott and others, 1981 ; Souther, in pressa). Age dates for the Lava Fork lavas (14C) are as young as 360+/-60 years BP (Souther, in press a). The Lava Fork volcanic rocks are spectacularly exposed and the lava field displays a wide variety of volcanological features including lava tubes and spatter vents."
"The main lava flow appears to have erupted from a vent located on a ridge of crystalline basement rocks at an elevation of 1400 m. The vent area is delimited by a thick blanket of black, glassy pyroclastic tephra which mantles bedrock and glaciers to the north, east and south."
"The main lava flows appear to have been erupted in a single period and were probably fed by lava fountains; the top surfaces of the lavas are occasionally covered with spatter agglutinate. The lava fountaining filled the cone with ponded lava, which eventually broke out, flowed across the ridge top, over a knob-like shoulder and down the steep valley wall to flood the valley floor below. This interpretation implies that the spatter bombs on the flanks of the cinder cone are part of the same eruptive activity that produced the lava flows."
"The main lava flow lies within the Lava Fork valley and, by damming the Lava Fork Creek, formed the two Lava Lakes. The southern limb of the lava flow extends south along the valley bottom for at least 20 krn into Alaska. Generally, the flow surface is scoriaceous and may have a thin veneer of clinkery material. Pahoehoe, ropy surfaces are common, and in places the lava flow has developed numerous, prominent lava channels with prominent levees (north fork of the lava at about 1040 m). The lava rivers commonly develop into lava tubes which subsequently have collapsed. In several localities, the lava tubes remain intact and are as high as 3 m and extend for 30-40 m."
From Hauksdottir and others (1994): “14C dating of a partly charred conifer log from the surface of one of the flows yielded an age of 360+/-60 BP (Table 1 [in original text], Elliott and others, 1981). Grove (1986) argued for an age of 130 BP based on 14c dating of material associated with the lower flows...Based on tree ring counts on living trees, and observations of the lava flow surface it is estimated to be around 150 years old. Living trees on the surface of an underlying flow give a minimum age of 350 years (B.C. Hydro, 1985)."
"A possible vent for the older flows is a tree-covered cinder cone located 4 km downstream of Blue Lake (B.C. Hydro, 1985)."
"The main lava flow appears to have erupted from a vent located on a ridge of crystalline basement rocks at an elevation of 1400 m. The vent area is delimited by a thick blanket of black, glassy pyroclastic tephra which mantles bedrock and glaciers to the north, east and south."
"The main lava flows appear to have been erupted in a single period and were probably fed by lava fountains; the top surfaces of the lavas are occasionally covered with spatter agglutinate. The lava fountaining filled the cone with ponded lava, which eventually broke out, flowed across the ridge top, over a knob-like shoulder and down the steep valley wall to flood the valley floor below. This interpretation implies that the spatter bombs on the flanks of the cinder cone are part of the same eruptive activity that produced the lava flows."
"The main lava flow lies within the Lava Fork valley and, by damming the Lava Fork Creek, formed the two Lava Lakes. The southern limb of the lava flow extends south along the valley bottom for at least 20 krn into Alaska. Generally, the flow surface is scoriaceous and may have a thin veneer of clinkery material. Pahoehoe, ropy surfaces are common, and in places the lava flow has developed numerous, prominent lava channels with prominent levees (north fork of the lava at about 1040 m). The lava rivers commonly develop into lava tubes which subsequently have collapsed. In several localities, the lava tubes remain intact and are as high as 3 m and extend for 30-40 m."
From Hauksdottir and others (1994): “14C dating of a partly charred conifer log from the surface of one of the flows yielded an age of 360+/-60 BP (Table 1 [in original text], Elliott and others, 1981). Grove (1986) argued for an age of 130 BP based on 14c dating of material associated with the lower flows...Based on tree ring counts on living trees, and observations of the lava flow surface it is estimated to be around 150 years old. Living trees on the surface of an underlying flow give a minimum age of 350 years (B.C. Hydro, 1985)."
"A possible vent for the older flows is a tree-covered cinder cone located 4 km downstream of Blue Lake (B.C. Hydro, 1985)."
References Cited
[1] Quaternary volcanic rocks of the Iskut River region, northwestern British Columbia, 1990
Stasiuk, M.V., and Russell, J.K., 1990, Quaternary volcanic rocks of the Iskut River region, northwestern British Columbia: Geological Survey of Canada Current Research Part E, Cordillera and Pacific Margin, no 90-1E, p. 153-157.[2] Recent basaltic volcanism in the Iskut-Unuk rivers area, northwestern British Columbia, 1994
Hauksdottir, S., Enegren, E.G., Russell, J.K., 1994, Recent basaltic volcanism in the Iskut-Unuk rivers area, northwestern British Columbia: Geological Survey of Canada Current Research no 1994-A, p. 57-67.Complete Eruption References
Recent basaltic volcanism in the Iskut-Unuk rivers area, northwestern British Columbia, 1994
Hauksdottir, S., Enegren, E.G., Russell, J.K., 1994, Recent basaltic volcanism in the Iskut-Unuk rivers area, northwestern British Columbia: Geological Survey of Canada Current Research no 1994-A, p. 57-67.
Quaternary volcanic rocks of the Iskut River region, northwestern British Columbia, 1990
Stasiuk, M.V., and Russell, J.K., 1990, Quaternary volcanic rocks of the Iskut River region, northwestern British Columbia: Geological Survey of Canada Current Research Part E, Cordillera and Pacific Margin, no 90-1E, p. 153-157.