GEO 155 1st Edition Lecture 25 Last Lecture Erosion on Slopes Outline of Current Lecture I Volcanoes a Background b Basalt c Andesite d Rhyolite e Other Hazards Current Lecture Where are they Spreading centers Hot Spots Subduction Zone How do they happen Type of eruption and landforms created depends on molten composition Spectrum o Basalt Low silicon High iron and magnesium Very hot Fluid These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute o o Dark color Oceanic Andesite In between characteristics of basalt and rhyolite Rhyolite High silicon Low magnesium and iron Less hot Viscous Light color Continental Basalt Shield Volcano Gentle eruption More liquid o Flows easily o effusive Relatively slow Broad gentle slope Example Hawaii s Big Island Flood Basalt Several vents close together Rare Andesite Cinder Cones More viscous o Can lead to clogged vent Explosive eruptions o Pyroclastic Cools as it erupts Small rocks and boulders Composite Cones Altervernating explosive or effusive eruptions o Explosive build loose cone o Effusive bind sediment Tall Example Mt Fuji Rhyolite Plug Dome Very viscous Can get cinder cones If flowing can t travel far High likelihood of eruption Other Hazards Nuee Ardent Clogged vent Can go miles in a few seconds o Pyroclastic flow Example Mt Pele Lahar Volcanic mudflow Mix of ash and water o Melted alpine glaciers post eruption storms Fast moving wet cement Tends to move toward valleys
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