EESA06H3 Lecture Notes - Lecture 5: Forearc
3 Mar 2012
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Document Summary
When oceans close is the dangerous volcanoes because of subduction. Iceland is very fluid not that dangerous, all gases come out. More viscosious - dangerous, stuff comes out pyroclastic. Volcanic bombs or ash(is a misnomer - named improperly) Pyroclastic broken by fire, rocks are shattered by eruptions and thrown up into air. The green areas subduction back into the mantle. The pacific ring of fire: tectonics of a closing ocean. Pacific rim - dense concentration of volcanes, major earthquakes, tsunamis. The stars marks earthquakes - the deepest earthquakes are. We know that slabs don"t melt till after 700km down. Magmatic arc a line of volcanoes directly above subduction zone. Oceanic crust made out of basalt. Silicic magma - sediment + seawater melted, reducing viscosiy of magma. Deep water trenches ocean floor going down into subduction zone. New zealand: small island, exposed tip of a much larger land mass (zealandia)
