tephra


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tephra

[′tef·rə]
(geology)
All pyroclastics of a volcano.
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Impact of tephra deposition on growth in conifers: the year of the eruption.
Processes included tephra fallout, pyroclastic density currents, multiple slope failures with debris avalanches and lahars, and interaction with the ice cap (Thouret et al, 1990).
Like other scholars, Reithofer traces indigenous notions of a time of darkness to the historical event of a volcanic eruption on Long Island in the Bismarck Sea in the 1600s, which darkened the sky with tephra airfall.
E., William 1983 Classic to Posclassic Tephra Layers Exposed in Archaeological Sites, Eastern Zapotitan Valley, en The Zapotitan Valley, Archaeology and Volcanism in Central America, Editado por Payson D.
The underlying ground isn't made of karst, but of loose, volcanic-rock particles called tephra. "This stuff is probably the most easily eroded sediment anywhere," says Kaufmann.
1980) and tephra deposits from the volcanically active nearby islands of Ambrym, Lopevi and Epi (Eissen et al., 1994; Robin et al.
Critically, the 1,000-yr-old replacements coincide with the eruption of a huge volcano in nearby Southern Alaska that deposited a thick layer of ash called the White River Tephra.
Three major ten'aces can be identified within the area: the river flats (180m above sea level (a.s.l.)), covered with recent alluvium (1000-.2000 years BP) and having flat to gently sloping topography; the Last Glacial terrace (200-240 m a.s.1.), covered with a mixture of loamy alluvium derived from a mixture of quarzo-feldspathic sediments, loess, and tephra (<15 000 years BP) overlying river aggradation gravels, and having flat to gently sloping topography; and an upper terrace (240-300m a.s.l.), covered with a mixture of loess and tephra (10000-25 000 years BP) and having flat, undulating, or rolling topography.
MATERIALS AND METHODS--The experimental site is located in the Comunidad Indigena de Nuevo San Juan Parangaricutiro in the northeastern region of Michoacan, Mexico, in a tephra deposit locally known as the Mesa de Cutzato (19[degrees]30'42.4"N, 102[degrees]12'03.0"W, 2,450 m elevation).
Gently sloping land is dominant; soils are generally well-drained, of low fertility, and derived mainly from rhyolitic alluvium and tephra. Vineyards are located on moderate slopes of 3[degrees]-5[degrees] (Fig.