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Volcanic Intrusions Steve Sparks (Earth Sciences )

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 )

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  1. Volcanic Intrusions Steve Sparks (Earth Sciences)

  2. Structure of eruption columns

  3. Volcanic plume dynamics H = 8.1Q0.25 Height of plume in km Q magma mass flux (thermal flux) Strong plume and weak wind

  4. Weak plumes: strongly wind affected

  5. 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

  6. Umbrella cloud dynamics

  7. Ungarish and Huppert, JFM 458, 283-301, 2002 Holasek et al. JGR 101, 635-655, 1996 Pinatubo 1991

  8. Exponential thinning (Thorarinsson & Pyle)

  9. 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

  10. 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

  11. 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

  12. 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

  13. Buoyancy and thin ash Layers Courtesy Peter Baines

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