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| Description: Volcanic Eruptions Factors that determine the violence of an eruption Composition of the magma Temperature of the magma Dissolved gases in the magma Viscosity of magma Viscosity is a measure of a material’s resistance to flow Viscosity of magma Factors affecting viscosity Temperature (hotter magmas are less viscous) Composition (silica content) High silica – high viscosity (e.g., rhyolitic lava) Low silica – more fluid (e.g., basaltic lava) Dissolved gases (volatiles) Mainly water vapor and carbon dioxide Gases expand near the surface Viscosity of magma Factors affecting viscosity Dissolved gases (volatiles) Provide the force to extrude lava Violence of an eruption is related to how easily gases escape from magma Easy escape from fluid magma Viscous magma produces a more violent eruption Materials Associated with Volcanic Eruptions Lava flows Basaltic lavas are more fluid Types of lava Pahoehoe lava (resembles braids in ropes) Aa lava (rough, jagged blocks) Gases One to five percent of magma by weight Mainly water vapor and carbon dioxide Picture Stats: Views: 244 Filesize: 3.12MB Height: 921 Width: 1184 Source: https://biology-forums.com/index.php?action=gallery;sa=view;id=39605 |