Any type of rock fragment that is forcibly ejected from the volcano during an eruption.
A general term used by volcanologists to describe all fragmental volcanic ejecta produced during explosive volcanic eruptions (Dehn and McNutt, 2000, p. 1271). This includes ash (<2mm diameter fragments), lapilli (2-64 mm diameter fragments and fragements greater than 64 mm in diameter known as bombs (semi-solid or plastic ejecta) or bombs (solid ejecta) (Tilling et al., 1987).
Tephra is a general term for fragments of volcanic rock and lava regardless of size that are blasted into the air by explosions or carried upward by hot gases in eruption columns or lava fountains. Tephra includes large dense blocks and bombs, and small light rock debris such as scoria, pumice, reticulite, and ash.
As tephra falls to the ground with increasing distance from a volcano, the average size of the individual rock particles becomes smaller and thickness of the resulting deposit becomes thinner. Small tephra stays aloft in the eruption cloud for longer periods of time, which allows wind to blow tiny particles farther from an erupting volcano.
Photograph by D. Wieprecht
Tephra erupted by Mount St. Helens on 18 May 1980 ranging in size from ash (left 2 piles) to lapilli (right 2 piles).
Photograph by E. Wolfe on 24 June 1991
Volcanic ash falls to ground and creates darkness, Mount Pinatubo in the Philippines.

Glossary of volcanic terms. - University of Wisconsin Oshkosh. . 2001.

Look at other dictionaries:

  • Tephra — is air fall material produced by a volcanic eruption regardless of composition or fragment size. [This is the broad definition of tephra (Greek tephra , ash ) proposed by the Icelandic volcanologist Sigurdur Thorarinsson in 1954, in connection… …   Wikipedia

  • Tephra — (gr.), so v.w. Asche …   Pierer's Universal-Lexikon

  • Tephra —   [griechisch »Asche«] die, , Petrographie: Sammelbezeichnung für alle unverfestigten vulkanischen Lockerprodukte (Aschen, Lapilli, Bomben u. a.). Aus ihnen entstehen die Pyroklastite …   Universal-Lexikon

  • tephra — [tef′rə] pl.n. [< Gr: see TEPHRITE] [with sing. or pl. v.] clastic volcanic materials, as dust, ashes, or pumice, ejected during an eruption and carried through the air before deposition …   English World dictionary

  • Tephra — Fossile pyroklastische Brekzie, Grand Teton Nationalpark, Wyoming Als Pyroklastische Sedimente, auch pyroklastische Ablagerungen oder Pyroklastika, werden in der Vulkanologie Ablagerungen bezeichnet, die zu mehr als 75% aus Pyroklasten bestehen.… …   Deutsch Wikipedia

  • Tephra — Éjecta Traduction à relire Piroclasto → …   Wikipédia en Français

  • tephra — /tef reuh/, n. (used with a pl. v.) clastic volcanic material, as scoria, dust, etc., ejected during an eruption. [1960 65; < Gk téphra (sing.) ashes] * * * …   Universalium

  • Tephra — Te|phra* die; <aus gr. téphra »Asche«> Sammelbez. für vulkanische Lockerstoffe …   Das große Fremdwörterbuch

  • tephra —    A collective, general term for any and all clastic materials, regardless of size or composition, ejected from a vent during a volcanic eruption and transported through the air; including ash [ volcanic; < 2 mm ], blocks [ volcanic; > 64… …   Glossary of landform and geologic terms

  • tephra — noun Etymology: New Latin, from Greek, ashes; akin to Sanskrit dahati it burns more at foment Date: circa 1944 solid material ejected into the air during a volcanic eruption; especially ash II,2b …   New Collegiate Dictionary

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