GEOL 306 Lecture Notes - Lecture 10: Effusive Eruption, Explosive Eruption, Magma Chamber
9 Feb 2018
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Document Summary
Rich in volatiles, especially water, during ascent to surface water wants to leave magma. Gas leaves magma efficiently (slow ascent), effusive eruption. If degassing is inefficient, bubbles explode, magma breaks and erupts violently. Andesitic lava does not flow rapidly but mound around the vent and flow slowly. Crust fractures into rubble called blocky lava. Lava flows remain close to the vent, can also form lava domes ash flow. Sometimes, dome can collapse due to gravity, creating block and. Block and ash flow: flow of mixture of ash and fragments, can be very dangerous. Dome can grow beneath the surface, cryptodome. Tephra (fragments of any size ejected during eruption) can. Deposit thickness and average particle size decreases away accumulate over meters from volcano huge volumes of debris. Explosive eruptions of intermediate to silicic magma generate. Porous pyroclast are called scoria or pumice (can float) Tephra: rock fragments (including pyroclasts) ejected into atmosphere during eruption. Tephra are usually transported via volcanic plumes.
