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EESA06H3 (563)
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Lecture 5

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Environmental Science
Nick Eyles

Lecture 5 y Volcanoes dangerous when Oceans close are the dangerous ones y Getting rid of old oceanic crust Pushing it down below continents melting it magma has a lot of silica so what happens to the rheology ability to flowhow easy it is for something to flow y Volcanic eruptionhow easy does the magma flow If it flows easy like Iceland and Kenya then volcanic eruptions are normalbecause lava is fluid y Dangerous volcanoes pyroclasticbroken by fire choke Rocks which are shattered by power of the eruption and blown up the earth up as bombs size of the rooms or as ash what we call a misnomery A misnomer is something named mistakenlyy Lots of volcanoes in Italy They thought it was product of coal on the ground burning so they use the term ash We know its not burned material but pulverized rocky Wax comes up and you get plumes Rising in the lava landy Light greenopposing motion where plates are going apart y Those cold red slabs shown in green go in the mantle They dont want go in the ground Friction happens Volcanoes happen y SA and NA moving to left Australia is moving up northwards In 70 million years Australia will be where modern day Tokyo is y Pacific rim of firedense concentration of volcanoes Major EQs like tsunamisy Tsunamisea floor is raised or lowered during an EQ and this pushes away seawater and comes as a wave y Subduction zoneoceanic crust going down Stars with different colors are EQs They are going down 700km is where deep EQs go y Tells us that these descending slabs maintain integrity until that depth and they melt and become plastic and you dont get EQs Long time for melting to happen y Magma coming up resulting in magmatic arcs Directly above subduction zone y Oceanic crust is made out of Basalt y Silicic magma is produced when we have enormous seawater and sediments in ocean that is melted y Has the ability to reduce viscosity of magmay New Zealand is a small island Exposed tip of a much larger land massLand mass is called zealanday Red line Pacific Rim is marking the boundary between pacific plate on the right and Australian plate on the left Over riding pacific plate y Teeth like marks indicate direction of subductiony Aussie plate is being subducted below pacific plate Up on top the pacific plate going down below Aussie plate In the middle of NZ there are volcanoes and major EQs No teeth on middle line means no subductiony Oceanic crust always gets subducted below lighter continental crust
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