GEOL 101 Lecture Notes - Lecture 6: Stratovolcano, Viscosity, Basalt
Document Summary
Magma viscosity: viscosity is the resistance of a liquid to flow. High viscosity= liquid flows with difficulty: volcanoes that erupt low viscosity magma have more gentle eruptions, volcanoes that erupt high viscosity magma have more violent eruptions. Very large, low structures that erupt low viscosity basaltic material (explosive eruptions: composite volcanoes: Moderately-sized cone-shaped structures that erupt higher viscosity andesitic material (non-explosive eruptions) Composed of lava flows and pyroclastic material: cinder cones (strato volcanoes): Small symmetrical cone-shaped structures that erupt cinders of various compositions (not usually explosive eruptions) Eruptive material: lava flows: basaltic lava: Aa= chunks of cool lava with liquid lava underneath. Pahoehoe= ropy smooth lava like its coming out of a tube. Crusts up on the outer surface but keeps flowing on the inner surface like a tunnel. Volcanic gases: 70% water vapor, 15% carbon dioxide, 5% nitrogen, 5% sulfur dioxide.
