I Volcanic Eruption Products a Lava flows a Determines lava type viscosity i Controlled by 1 Silica 2 Temperature 3 Crystals ii Basaltic lava flows Low viscosity 1 2 Flow 30 km hour 3 Thin widespread 4 Two types a Pahoehoe b Aa 5 Features Lava tubes a b Columnar jointing c Pillows iii Andesitic flows Increased viscosity 1 2 Flows 1 5 m day 3 Moves as jumble of blocks b Pyroclastic debris iv Rhyolitic flows 1 High viscosity 2 Domes v Lava fountains i Ash ii Lapilli or cinders 1 Pele s hair 2 Pele s tears iii Blocks iv Bombs v Pumice vi Pyroclastic flow Ignimbrite 1 2 Ex 1902 Mt Pele vii Lahar 1 Ex 1985 Nevada del Ruiz viii Pyroclastic deposits 1 Tephra a Unconsolidated a Cemented tephra 2 Tuff 3 Ignimbrite c Volcanic gas i Up to 9 of magma ii H2O CO2 H2S SO2 iii Low viscosity magmas 1 Bubbles rise faster than magma a Dissipate into atmosphere 2 Trapped in magma 3 Vesicles iv High viscosity magmas 1 Gas cannot escape II Volcanic Architecture a Magma chamber b Conduit c Edifice d Crater e Caldera i Upper crust 1 Solidify or erupt i Fissure ii Vertical pipe i Debris accumulates ii Forms cone or mound i Central depression ii Summit collapses into conduit iii 500 m diameter i Thousands of meters in diameter ii Hundreds m deep iii Core of volcano collapses f Resurgent dome III Volcano Morphologies a Shield volcanoes b Cinder cones i Basalt ii Gentle slopes iii Long broad i Tephra deposits ii 30 35o slope iii Symmetrical c Stratovolcanoes i Felsic ii Layers of lava tephra iii Large steep and cone shaped IV Eruptive Style a Effusive i Lava flows 100s km ii Basaltic b Explosive i Debris avalanches ii Trapped gases iii High pressure c Phreatomagmatic eruption i Contact with water d Krakatau i Largest explosion in recorded history ii 5000x greater than Hiroshima iii Explosion heard about 4800 km away e Controlled by i Viscosity 1 Flow length ii Gas pressure iii Environment 1 Heat retention V Hot Spot Eruptions a Oceanic settings i Shield volcanoes 1 Thousands of thin basalt flows depresses crust 2 Submarine portion slumps a Tsunamis b Continental settings i Basaltic and rhyolitic magmas c Flood basalts i Hot spot underlies rift ii Decompression melting combined with a mantle plume iii Huge amount of magma formation 1 Most active mid ocean ridge above sea level VI Volcanic Hazards d Mid ocean ridges i Where most volcanoes are found ii Most active lava production iii Iceland e Convergent boundaries i Most subaerial volcanoes ii Associated with subduction zones iii Magma generated iv Ring of Fire f Continental rifts i Partial melting of both mantle and crust a Basaltic lava effusive eruptions i Mostly property damage not deaths b Ash pumice and lapilli falls i Threat to machines ii May contain toxic compounds iii Biggest threat to airplanes c Pyroclastic flows i 300 km hour ii Instant death iii Heat and toxicity iv Flatten buildings d Eruption blast e f Landslides Lahars i Water ash and other debris ii Extremely destructive iii Speeds greater than 50 km hr iv Especially destructive and deadly at snow covered volcanoes g Earthquakes h Tsunamis i Gas emissions VII Predicting Volcanic Behavior a Based on recurrence interval b Most volcanoes i Sporadic ii Time between eruptions few years to millenia c Signals i Change in heat flow ii Change in shape iii iv Increase in seismic activity earthquakes Increase in gas steam d Assessment maps e Evacuations f Diverting flow VIII Volcanoes Beyond Earth a Craters on the moon b Venus i 22 000 volcanic edifices c Mars i Olympus Mons largest volcano in solar system