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Volcanic Intrusions Steve Sparks (Earth Sciences ). Structure of eruption columns. Volcanic plume dynamics. H = 8.1Q 0.25. Height of plume in km Q magma mass flux (thermal flux). Strong plume and weak wind. Weak plumes: strongly wind affected. High Intensity eruptions (stratosphere).
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Volcanic Intrusions Steve Sparks (Earth Sciences)
Volcanic plume dynamics H = 8.1Q0.25 Height of plume in km Q magma mass flux (thermal flux) Strong plume and weak wind
High Intensity eruptions (stratosphere) Mount St Helens 1980 16 km Wind ~ 33 m/s Lascar 1993 23 km wind 15 m/s Umbrella cloud expansion increasingly dominates as intensity increases
Ungarish and Huppert, JFM 458, 283-301, 2002 Holasek et al. JGR 101, 635-655, 1996 Pinatubo 1991
Exponential thinning (Thorarinsson & Pyle)
Ash transport in umbrella cloud Hazens law: ash well mixed by internal turbulence C = Coexp[-pV(r2- ro2)/Q] V is terminal velocity, Q is is volume flux into umbrella r is radial distance from vent ro is umbrella corner radius
1815 Tambora distal ash fall Combine ash falling out while the cloud advances and ash depositing once the eruption stops: C1 = C0exp [-B(r2-r02)] vs C2= 2BrC0exp [-B(r2-r02)] -> dependent on eruption duration and particle fall velocity Thanks to JessyKandlbauer
Giant co-ignimbrite clouds from very large magnitude eruptions (M>6.5) Coriolis gravity balance Baines and Sparks, GRL, 2005 Oppenheimer Quat. Sci. Rev., 2002
1315 Kaharoa eruption Distal ash transport in the atmosphere Advection-diffusion models e.g. TEPHRA 2: deposit NAME III: suspended ash Particles fall out by settling and dispersed by atmosphere. No internal buoyancy and no plume dynamics Bonadonna et al., JGR, 2005
Buoyancy and thin ash Layers Courtesy Peter Baines