EESA06H3 Lecture Notes - Lecture 5: Oceanic Crust, Pacific Plate, High Island
Document Summary
When ocean"s close: magama has slicar . lots of stuff blown up into air and sudden release of gas pyroclastic depris (fire/break) volcanos use a lot of ash. Floor of pacific ocean is being pushed down : subduction zones and continents are moving in. Continents that are growing around the crust are subducted . at the expense of the ocean. Magma moves up and picks up silica destroyed volcanoes and continents grow in result. Adding to continues while recycling oceanic crust. Density: driving plate underneath(heavier crust goes down ) Japan is island arc: embryonic continent : how first crust started four billion years ago-> magma ocean earth a huge red ball . Thought ocean water came out of magma ->subduction. Tsunamis, sea floor falling and sea water displaces because sediment is scraped. Volcanic island arcs: where oceanic crust is subducted below other oceanic crust merapi volcano-indonesia;s most dangerous and active made up of jojned up volcanoes steep and unstable and collapse.
