EARTH121 Chapter 4, 10, 14, 20: EARTH 121 Textbbok Notes - MIDTERM 2 (Chapters 4, 10, 14, 20)
28 Nov 2017
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Magma composition, texture and the amount of dissolved gasses it contains determines whether a volcano extrudes magma violently or gently. Importance of dissolved gasses: volatiles tend to increase the fluidity of magma, eruption columns: highly viscous magmas that expel jets of hot, ash-laden gases that evolve into buoyant plumes. The viscosity of magma plus the quantity of dissolved gases and the ease with which they can escape, determine the nature of a volcanic eruption. They develop in the interior of a lava flow where the temperatures remain high long after the surface congeals. Gases: volatiles are held in magma by confining pressure. Lahars: mudflows on active and inactive volcanoes: destructive flows that occur when 1. volcanic debris become saturated with water and rapidly move down steep volcanic slopes or 2. When heavy rainfall saturates weathered volcanic deposits: can occur when a volcano is not erupting.
