GEOL 106 Lecture Notes - Lecture 6: Return Period, Subduction, Seismometer

• School: Queen's University
• Department: Geological Sciences and Geological Engineering
• Course: GEOL 106
• Professor: Ryan Dhillion

Document Summary

Most activity concentrated along major plate boundaries. Risk depends on the types of volcanoes. Vesuvius in italy, skaptar j kull, in iceland, nevado del ruiz in. Most active volcanoes located near plate boundaries. 2/3 active volcanoes situated on ring of fire . How magma forms: come the asthenosphere, 3 main ways can melt silica. Viscosity affects flow of lava and therefore shape of: volatile content determines how explosive the eruption will be. Increase silica = increase viscosity (generally: in explosive eruptions, tephra is ejected. Occurs at divergent plate boundaries, continental rifts, hot spots. Chemical compounds that lower melting temperature of rock. Magma properties: composed of melted silicate minerals and dissolved gas, volcanic rocks named depending on the amount of silica present in the rock. Rhyolite: different shapes and eruptive styles are influence by the, shield chemistry (silica content) and viscosity of magmas. Gentle arch, or shield shape, with shallow slopes and built up of many lava flows.