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- noun Plural form of
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I walked by a number of posters on ocean sediments — Thornalley; Jian Yu MD01-2378, SO185-10460 in the China Sea; poster PP1598; 1773 showed tephras MD99-2275.
In addition to the tephras found in all or most of the sites, there are several tephras that can only be found in one or two of the lake basins studied.
The lack of tephras in the sediment cores of this study that are correlatable with any of the numerous proximal tephras deposited during the last two millennia Hall and Mothes, 1994 suggests that the eruptions that produced the distal tephras noted in this study were either especially large or occurred when wind directions were favorable to transport tephras at least 150 km to the south.
In either case, the distal tephras noted in this study are the product of an unusual set of circumstances, which have not been repeated in the past ~2000 yr: unusually voluminous eruptions, strongly prevailing southward winds, or both.
Six widespread tephras ~0.1–1.0 cm thick with rhyolitic to dacitic glass and/or phenocrysts of feldspar or hornblende are preserved in the glacial lakes of Las Cajas National Park, southern Ecuador.
The widely recorded tephras were deposited 9900, 8800, 7300, 5300, 2500, and 2200 cal yr B.P.
Here we report the first such evidence in the form of thin (à⣃’à⺰.1 to 1.0-cm-thick distal tephras deposited in glacial lakes and peat lands in Las Cajas National Park (Fig.