GG231 Chapter Notes - Chapter 4: Pyroclastic Surge, Pyroclastic Rock, Crater Lake
Document Summary
Mount unzen, 1991: most destructive of japan"s 19 active volcanoes, 200 years ago erupted and killed 15 000 people, june 3, 1991 erupted forced 12 000 people to evacuate. End of 1993 produced 0. 2 km3 of lava and more than 10 000 superheated flows of hot gas, ash and large rock fragments. Produced lahars, special channels constructed to contain them. Introduction to volcanoes: located near plate boundaries, 2/3 of all active volcanoes on land located along ring of fire, volcanoes lie above subduction zones bordering pacific, nazca, cocos, philppine and juan de fuca plates, magma. Composed of melted silicate minerals and dissolved gasses. Si and o most abundant, creating silica (sio2) Rhyolite >68% sio2 (most rare: volcano types. Different shapes and eruptive styles based on viscosity of magma. Magma with higher silica content are more viscous than magma with low silica content. Low silica content tend to explode (basalt/andesite)