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Atka volcanic complex reported activity





Event Name : Atka CFE-Big Pink

Start: 300000 Years BP Hydration rind - glass
Stop: 500000 Years BP Hydration rind - glass

Lava flow: BibCard
Caldera/crater: BibCard BibCard
Eruption Type:Effusive
MaxVEI: 4 BibCard
Eruption Product: dacite BibCard

Description: From Meyers and others (2002): "After this initial activity, the central cone, Atka Volcano, grew on top of the shield and probably reached an elevation of ~2,200 m. A series of satellite vents then formed, ringing the central cone (Fig. 2 [in original text]). These volcanic edifices are comprised of lava flows as well as pyroclastic units including many lahars. The increase in the abundance of pyroclastic rocks as well as the change in the dominant lava from basalt to andesite differentiates these later volcanic vents from the earlier, shield building stage. Summit glaciers have breached many of the summit craters, thereby forming active cirques which dissect many of the satellite vents."

"Ancestral Atka Volcano subsequently collapsed, creating a caldera 5 km in diameter (Fig. 2 [in original text]). Associated with this event was the eruption of a large dacitic flow (Fig. 3 [in original text]). This flow, called Big Pink because of its distinctive field appearance, is approximately 400 m thick, nearly oval in outline and 2-3 km in maximum dimension (Fig. 2 [in original text]). It consists of pumiceous and glassy units but is not associated with any ash flows. A hydration date from Big Pink suggests the caldera-forming eruption of ancestral Atka Volcano occurred 300,000 to 500,000 years ago (Marsh, unpublished data). A series of NW-trending dikes cuts the entire Atka Volcano shield and was presumably emplaced during caldera formation (Fig. 2 [in original text]). The dikes are nearly vertical and approximately 1 m thick."

The Global database on large magnitude explosive volcanic eruptions (LaMEVE; 2016) reports a magnitude of 4.0, bulk eruptive volume of 0.10 cubic km and a dense rock equivalent eruptive volume of 0.040 cubic km for the eruption.

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Page modified: March 30, 2017 14:36
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