GEO 1111 Lecture Notes - Lecture 11: Cinder Cone, Volcanic Arc, Igneous Rock

• School: University of Ottawa
• Department: Geology
• Course: GEO 1111
• Professor: Robert Jack Cornett

Document Summary

Volcanic activity along plate margins: spreading centers, greatest volume of volcanic rock is produced along the oceanic ridge system (divergence, mechanism of decompression melting. An island arc if in the ocean. A volcanic arc if on a continental margin. Both are andesitic (intermediate composition: most of the worlds explosive volcanoes. Intraplate volcanism: activity within a tectonic plate, associated with plumes of heat in the mantle, form localized volcanic regions in the overriding plate called a hotspot. Mafic and felsic magmas have very different physical properties. The viscosity of a magma is a functions of temperatures silica content an volatile content. Mafic larger, lower viscosity lava flow, less explosive, low ratio of pyroclastic sediment to lava, low-relief volcanoes (shield) Felsic/intermediate smaller, higher viscosity lava flow , explosive, high ratio of pyroclastic sediment to lava, steep volcanoes. Felsic: si-rich , very viscous, high h20 and gas. Mafic (basalt: low-si = much more fluid like, types of basaltic flow.