Around the same time, a massive volcanic eruption in the Wrangell Mountains in Alaska occurred, blanketing the area in a layer of ash, up to a foot deep, called the White River tephra.
大致在同一时期，阿拉斯加州的弗兰格尔山脉出现了大规模的火山爆发，这个地区遂被深达一英尺的怀特河火山灰所覆盖。
Tephra is any fragmented material produced by a volcanic eruption, be it ash or rock.
无论是灰烬还是岩石，所有因火山爆发而形成的碎片状物质都称作火山灰。
Significant changes in phytolith assemblages occur at the same depth as four major tephra. indicating a sharp decline in trees and shrubs and a surge in grass and Cyperaceae.
植硅体组合在4个主要的火山灰层都发生了明显的变化，表现在树木和灌木的急剧下降及禾草类和莎草科的繁盛。
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