EARTHSC 2GG3 Study Guide - Final Guide: Coriolis Force, Jet Stream, Ath

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Pyroclastic flow: mixture of hot volcanic ash and steam that pours downslope because it is too dense to rise. Can be referred to as an ash flow, glowing avalanche or ignimbrite deposit. Flows develop when rapidly erupting steam carries large volume of ash in a column that rises high above the volcano. When the rush of steam slows, part of column collapses and the cloud of ash pours down the flank of the volcano. Less dense part billows above as loose ash is stirred into the turbulent air. Fast-moving flows tend to hug valley bottoms but their high velocity can carry them over intervening hills and ridges. Destroys everything flammable in their path (including forests and people) Can race across ground ahead of a pyroclastic flow. Commonly originate as lateral blasts of ash and steam in the first stage of an ash-flow eruption. Because of their large proportion of steam they are generally less dense than standard pyroclastic flows.