geology_15 - Chapter 6: Volcanic Activity Introduction: ~...

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Chapter 6: Volcanic Activity Introduction: ~ 1,500 active volcanoes on Earth 400 erupted in the last century ~ 50 eruptions per year Most activity concentrated along major plate boundaries Impact risks depend on the types of volcanoes ~ 500 million people living near volcanoes 100,000 deaths during the last 125 years 23,000 in the last 20 years Densely populated countries in the volcanic zones (e.g., Philippines, Indonesia, Japan, Mexico) Some major cities are located near volcanoes Volcanism in space: Highly related to plate tectonic movement Concentrated along the Pacific ring of fire In the United States: Alaska, Cascades, and Hawaii Three types of magma: The composition of magmas and lavas is controlled by the most abundant elements in the Earth Si, Al, Fe, Ca, Mg, Na, K, H, and O Three distinct types of magma are more common than others: Basaltic , containing about 50 percent SiO2 Andesitic , about 60 percent SiO2 Rhyolitic , about 70 percent SiO2
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This note was uploaded on 04/08/2011 for the course GEOL 2001 taught by Professor Babaie during the Winter '09 term at University of Georgia Athens.

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geology_15 - Chapter 6: Volcanic Activity Introduction: ~...

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