pyroclastic flow

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pyroclastic flow,

turbulent, fluidized mixture of rock, volcanic ash, and hot gas that moves like an avalanche away from a volcanic eruption. A pyroclastic flow may contain a mix of rock fragments ranging up to the size of boulders, with the heavier fragments moving along closer to the ground. The hot, expanding gases suspend ash and smaller rock particles, which can then support larger rock fragments; a lack of friction among the particles enables the mixture to travel great distances.

A flow may result from the collapse of the eruption column of a volcano or the collapse of a lava dome or lava flow. Flows that result from an eruption-column collapse are dominated by pumice and move more rapidly; flows can travel as fast as 100 mph (160 kph), reach temperatures that exceed 900°F; (500°C;), and in some instances climb slopes and cross stretches of open water. The speed at which they move, the heat and toxicity of their gases, and the debris that they carry make pyroclastic flows extremely destructive and deadly. A pyroclastic flow from the 1902 eruption of Mt. Pelée on Martinique killed nearly all of the 28,000 inhabitants of Saint-Pierre.

pyroclastic flow

[¦pī·rə¦klas·tik ′flō]
Ash flow not involving high-temperature conditions.
References in periodicals archive ?
Key words: caldera, eruption unit, ignimbrite, domes, magmatic eruption, phreatomagmatic eruption, pyroclastic flow, pyroclastic surge.
He likewise said that the Miisi Gully was also the path of the pyroclastic flow Monday evening.
PIVS also shared some photographs of the pyroclastic flow from Monday morning on its Facebook page.
The block-and-ash pyroclastic flow and surge deposits (IN) are exposed in La Salvia, being 5 m thick (Fig.
Solidum noted two scenarios: first, the volcano as it now continues to exhibit lava fountaining events, ash plumes, lava flow, pyroclastic flows and second, blockade over the volcano or gas pressure and magma buildup that could trigger a big explosion.
The approach worked for water-saturated mud flows--we thought that maybe it would work for pyroclastic flows,' said Barry Voight, professor emeritus of geosciences at Penn State University.
Pyroclastic flow, a fast-moving current of hot gas and volcanic matter, were deposited 4.
If you don't mind me mixing my metaphors, you're looking at a woman swept up in a pyroclastic flow.
A pyroclastic flow consists of hot rocks, ash and superheated gases that rapidly flow down from the area of dome collapse on a volcano.
At a cut in the Quebrada Higuera, they found Hule tephra resting discordantly on a wood-bearing pyroclastic flow from Volcan Congo.
Experts worry that such a powerful eruption could by accompanied by a pyroclastic flow, a searing mix of gas and rock that races down the mountain incinerating everything in its path.
Legazpi City, Albay -- State volcanologists said yesterday that the restive Mayon Volcano will continue to exhibit small eruptions and lava fountaining or even a major blast and pyroclastic flow for the next 2-3 months, at least.