Volcanoes - Lesson 5 - Part 6 of 7

Volcanoes - Lesson 5 -- Part 6 of 7 •Gases dissolved in magma ; gas important to contribution to the early atmosphere and the oceans •Explosive release of gas causes the violence; rocks associated with violent volcanoes; pyroclastic rock , volcanic bombs, Volcanic ash, pumice •NWT shows ancient Precambrian rock, ancient tuff •Cross-section shows why dykes are related to the composition in the rocks •Violence of eruption; very explosive, less explosive •Very explosive -- Composite cone (mt fugi) release of gas, •Caldera -- release an enormous amount of gas •Krakatoa is a Caldera •B&W footage showing Krakatoa mini exposion •Dark material fragmented pumice and ash, steam shown from the heating of the sea water. •Crater lake in Oregon small caldera, •Kilauea another Calera very active volcanic area •Footage showing seismology on Kilauea, movement of the magma