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Iskut-Unuk River cones reported activity



Event Name : Iskut-Unuk River cones 150 yBP

Start: 150 Years BP Tree ring
Stop: 70 Years BP Tree ring

Lava flow: BibCard
Eruption Type:Effusive

Description: From Hauksdottir and others (1994): "The youngest flow erupted from a vent located on a ridge on the eastern side of Lava Fork valley. The lava flowed south, along the valley and southeast along Blue River valley, damming the river and forming Blue Lake. Near the main vent, the volcanic rocks overly basement rocks, including foliated biotite-quartz-schist intruded by granodiorite."

"Near its source, the youngest lava flow has ropey pahoehoe surfaces and forms well-developed small lava channels and lava tubes. Spatter, cinder and ash are abundant around the vent. Downslope and away from the vent, the flow surface abruptly changes to aa and splits into two main streams (north and south forks). The lava streams form large channels (Fig. 10 [in original text]) with several generations of prominent levees. Accretionary lava balls are common on the flow surface of the north fork lava (Sta. 23). They are approximately 5 m in diameter and consist of a red cinder breccia coated by massive flow which exhibits radially oriented irregular jointing. Xenoliths of basement rocks occur in both the interior and exterior portions of the lava balls."

"Grove (1986) argued for an age of 130 BP based on 14c dating of material associated with the lower flows. Subsequent dating, using tree-ring counts, gives a minimum age of 70 years old for the youngest flow (B.C. Hydro, 1985). Based on tree ring counts on living trees, and observations of the lava flow surface it is estimated to be around 150 years old."

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Page modified: March 30, 2017 14:36
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