EOSC 114 Chapter 6: Volcanoes
24 Feb 2015
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Document Summary
Volcanoes that have well-formed aesthetic conical shape = active. Most famous volcano is vesuvius (italy), at the subduction of mediterranean seafloor. Plinian eruption = blows ash to great heights and volcanic gases. Lahar = gravity-pulled mass movements of muddy volcanic debris. Differences in oxide percentages produce magma of variable compositions and behaviours. If the magma cools and solidifies below the surface it is known as plutonic rock or intrusive. If magma reaches the surface it is known as volcanic rock or extrusive rock. Water concentration in these magma plays a controlling role, followed by viscosity. Magma contains dissolved gases hed as volatiles. Their solubility increases as pressure increases and as temperature decreases. High viscosity magma = harder for gas bubbles to escape. Highly viscous; sometimes not flowing effects on viscosity of magma: higher temperature lowers viscosity, silicon and oxygen increase the viscosity, increasing content of mineral crystals increases viscosity. Spreading centres have all the factors to produce a peaceful eruption.
