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Igneous Structures: Intrusive. Viscosity. Units: pascal-seconds (kg/m-sec) How many pascals pressure x how many seconds to squash fluid flat? Viscous: Material flows as long as pressure is applied, however small Pseudoviscous: Material flows after some threshold stress.
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Viscosity • Units: pascal-seconds (kg/m-sec) • How many pascals pressure x how many seconds to squash fluid flat? • Viscous: Material flows as long as pressure is applied, however small • Pseudoviscous: Material flows after some threshold stress
What Drives Magma? • Magma is typically 10% lighter than equivalent solid rock • Why pressure inhibits melting • Buoyancy drives magma upward • Weight of rock around volcanic conduit > weight of magma • Gas pressure powers volcanic eruptions • Mafic (dense) rocks can sink in crust by viscous flow