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Aniakchak reported activity





Event Name : Aniakchak Vent Mountain lava and tephra

Start: 400 Years BP Tephrochronology
Stop: 1931 Tephrochronology

Lava flow: BibCard BibCard
Tephrafall: BibCard BibCard
Pyroclastic flow, surge, or nuee ardente: BibCard
Lava dome: BibCard
Eruption Type:Explosive

Description: From Bacon and others (2014): "Vent Mountain scoria and spatter cone is the most prominent topographic feature within the caldera (figs. 10, 12Cand 12D [in original text]). The cone rises 440-530 m above the caldera floor to an elevation of 3,350 ft (1,021 m). The 210-m-deep summit crater has a diameter of ~800 m. Numerous blocky lava flows emanate from the cone's lower flanks and from a prominent fissure vent that cuts the southwest flank. Although some outcrops of basaltic andesite and mafic andesite lava west of The Gates and in the larger maar crater possibly had source vents now hidden beneath Vent Mountain, the majority of products attributed to that volcano are silicic andesite and dacite."

"The youngest Vent Mountain lavas emanate from the south fissure vents, draping the south flank between lobes of earlier lava and spreading out from the southwest and south bases of the Vent Mountain edifice to pond against the caldera wall. One of these flows incised a channel into a small glacier and descended to the northeast through New Cone crater to overlap earlier Vent Mountain lava. Tephra from multiple eruptions at the summit, the south fissure, and New Cone blankets the west, south, and east flanks of the Vent Mountain edifice. The youngest products of Vent Mountain are agglutinated spatter plastered on the north side of the cone and a small lava dome in the summit crater. The total volume of Vent Mountain lava and tephra probably exceeds 1.5 km. If the radiocarbon constraint on New Cone is correct, much of Vent Mountain lava was erupted since ca. 400 yr B.P. The youngest flows and agglutinate predate only the 1931 eruption."

From Neal and others (2001): "Two young, but prehistoric, explosive events at Aniakchak occurred closely spaced in time about 400 years BP. The first is inferred to have originated from the flank of Vent Mountain, a prominent intracaldera cone (cover photo; fig. 5 [in original text]). This eruption dispersed energetic pyroclastic surges within the caldera and fallout to the north and northeast of Aniakchak."

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