Volcanic Hazards

Geoff Mackley

Tephra Collective term for all airborne or groundflowing pyroclasts including solidified magma. Tephra is classified according to size: Bombs: > 64mm diameter Lapilli 2-6mm diameter Ash <2mm diameter

Lava Shield – Low Viscosity (flows far) Cone – high Viscosity (explosive, cools quickly) Not usually a major hazard, flows in channels or is slow enough to move away from it

Lava Bomb Molten rock, ranging in size from stones to house sized boulders. Explode out of cone volcanoes and can travel many miles

Pyroclastic Flow Superheated gas cloud cascades down the mountain at speeds of up to 450 miles per hour https://www.youtube.com/watch?v=Cvjwt9nnwXY

Ash Ash causes many issues. It can destroy engines such as in aeroplanes due to its glass like structure. It causes breathing difficulties, destroy crops and can collapse roofs

Steam Not usually a major hazard, but can cause ash to be propelled very high and travel greater distances

Gas Mainly CO2 and SO2. Toxic and can kill people, animals and plants

Lahar Ice from the top of a volcano (or heavy rain) mixes with ash to form a raging river of mud that can bury entire towns