ESS 101 Lecture Notes - Lecture 4: Subduction, Vestmannaeyjar, Heimaey
15 Apr 2016
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Document Summary
The nature of volcanic hazards is strongly tied to viscosity and gas content of the magma. Basaltic composition eruptions tend to be non-explosive (effusive: basalt has low viscosity - very fluid. Gas escapes easily: basalt has low gas content, loss of life = rare in effusive explosions ; more damage to structural things that can"t move because there will be greater lava flow. Basaltic eruptions happen at different tectonic settings around the world: four different locations. Iceland sits on a basaltic spreading ridge - hotspot. Pyroclastic eruptions (explosive) - most devastating volcanic eruptions: more human casualties. Vesuvius had cataclysmic pyroclastic eruption in 79 ad: two phases: Gas pressure builds up as magma rises. Hot material is then ejected into the air. Because of its composition and high density, it falls: dense clouds of super-heated gas and ash fall down the flanks at 100-160 km/hr.
