EOSC 114 Lecture Notes - Lecture 11: Strombolian Eruption, Volcanic Glass, Phreatomagmatic Eruption
30 Jan 2018
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Document Summary
Two main styles: effusive outpouring of molten magma from the vent lavas, explosive gas driven violent eruptions pyroclastic deposits. Passive eruption of magma: lava flows (mafic-intermediate, lava domes (felsic-intermediate, gravitational collapse of lava flows/domes. Outer crust cools and solidifies insulating the molten interior. Explosive: buoyant eruption column of ash, pyroclastic airfall -> when the ash starts to fall, pyroclastic flows (column collapse) -> parts of column can collapse = makes a flow, blocks and bombs proximal to vent. Pyroclastic fall: eruptio(cid:374) (cid:272)olu(cid:373)(cid:374)s: (cid:1005)(cid:1004)"s of k(cid:373)s, widespread distribution of ash in the downwind direction, ash blankets topography . Why gas matters: magma produces bubbles (gas exsolves) during ascent, bubbles expand as the magma rises (lower p, foaming explosivity. Depends on: amount of bubbles, rate of rise, bubble retention. In magma chamber bubbles are in solution as they rise they expand and then they fragment. Increasing bubbles = decreasing viscocity = increasing speed of rise of the mamgma.
