Lecture 5 y volcanoes dangerous when: oceans close are the dangerous ones. y getting rid of old oceanic crust. Iceland and kenya then volcanic eruptions are normal ? because lava is fluid. y dangerous volcanoes (pyroclastic-broken by fire) choke. 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 rock. y wax comes up and you get plumes. Rising in the lava land. y light green-opposing motion where plates are going apart. y those cold red slabs (shown in green) go in the mantle. Volcanoes happen. y sa and na moving to left. In 70 million years, australia will be where modern day tokyo is. y pacific rim of fire-dense concentration of volcanoes. Major eqs like tsunamis. y tsunami-sea floor is raised or lowered during an eq and this pushes away seawater and comes as a wave. y subduction zone-oceanic crust going down.