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    ash and tephra falls, which type of volcano the hazard occur?

    ash and tephra falls, which type of volcano the hazard occur?

    0  Views: 469 Answers: 1 Posted: 10 years ago

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    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. Such fragments range in size from less than 2 mm (ash) to more than 1 m in diameter. Large-sized tephra typically falls back to the ground on or close to the volcano and progressively smaller fragments are carried away from the vent by wind. Volcanic ash, the smallest tephra fragments, can travel hundreds to thousands of kilometers downwind from a volcano.


    Read more :http://volcanoes.usgs.gov/hazards/tephra/



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