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Parameters & Protocol 

 

 

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Model Parameters and Protocol

The workshop and the model runs resulting from it will focus on a specific interval in volcanic eruptions, starting with host magma and bubble/crystal nucleation, and ending with fragmentation in the eruptive conduit. Atmospheric eruption clouds depend largely on pre-eruptive magma dynamics, but are a separate and complex issue, so will not be addressed at the workshop. Also, magma generation and lithospheric migration are not considered, but the existence of volatile-saturated magma are the standard starting point for the workshop.

We invited a key expert laboratory analysis and/or observations in each of these areas to ensure that the best values and formulations are used by the participating models as basic input and environmental conditions.

Content -

bulletRhyolite Parameters
bulletBasalt Parameters
bulletModel Output Protocol

PARAMETER LIST

This table indicates parameters to be standardized as input to volcanic models. Not all models consider all of these explicitly.

Rhyolite

PROPERTY VALUE FORMULAS SENSITIVITY STUDY TASK LEADER REFS COMMENTS
Melt composition C-A Rhyolite;
Mono Crater		 Mono Crater Rhyolite X Rutherford Newman et al., 1988, Am. Mineral.  
Volatile chemistry Water          
Volatile concentration and solubility    Zhang's formula   Zhang Zhang, 1999, EPSL Saturation  initial water content
Initial concentration From P, T, X     Anderson    
Crystal nucleation

0

   X      
Speed of sound  

         BmBg
c2= -------------
     r[(1-f)Bg + fBm]

   Mitchell    
Melt bulk modulus Bm     Papale    
Crystallinity 

0

   X      
Temperature (initial and evolution) 850˚C rhyolite   X Mastin   Isothermal
Thermal diffusivity 0.8 x10-6 m2/s     Dingwell Bagdassarov et al. 1996  
Water diffusivity   Zhang's formula X Zhang Zhang and Behrens, 2000  
Melt density    f(T, P, X)   Dingwell Dingwell, 1998  
Pressure  200 Mpa until sonic or 1 bar at vent   X Massol     
Rheology    f(T, X, strain rate) X Dingwell Hess and Dingwell, 1996  
Magma rheology     X   Llewellin et al., 2002 Use capillary number
Bubble number density 1015 m-3          
Nucleation  None   X Gardner     
Coalescence  None   X Larsen     
Bubble size distribution Monodisperse   X Mangan     
Fragmentation threshold   me=S=25 MPa X Navon     
Post fragmentation particle size 200 micron   X Bergantz    
Surface tension     X Dingwell Bagdassarov et al., 2000  
Geometry (vent, conduit, chamber) Cylindrical;
50 m diameter;
8 km base		   X Mitchell, Gaffney    
Country rock characteristics Rigid, impermeable,
2551 kg/m3		     Starostin    
Recharge from below Output to maintain steady-state     Bergantz    
Transient     X      
Trigger  None   X Koyaguchi    
Drag coefficients; 2-phase flow parameters Smooth walls, no slip, model at will     Papale    
 

Basalt

PROPERTY VALUE FORMULAS SENSITIVITY STUDY TASK LEADER REFS COMMENTS
Melt composition Etna Basalt Trachybasalt X Rutherford Newman et al., 1988, Am. Mineral.  
Volatile chemistry Water, CO2 4:1          
Volatile concentration and solubility    Solubility curves   Papale Papale, 1997, 1999 Saturation  initial water content
Initial concentration Water = 2 wt%
CO2 = 0.5 wt%		     Papale    
Volatile equation of state Water - ideal
CO2 - ideal		     Papale    
Crystal nucleation

0

   X      
Speed of sound  

         BmBg
c2= -------------
     r[(1-f)Bg + fBm]

   Mitchell    
Melt bulk modulus Bm     Papale    
Crystallinity 

0

   X      
Temperature (initial and evolution) 1100˚C basalt   X Rutherford Buettner et al., 1997 Isothermal
Thermal diffusivity 0.8 x10-6 m2/s     Dingwell Watson, 1994  
H2O diffusivity   Zhang's formula X Zhang Zhang et al., 1991  
CO2 diffusivity   Provided by Zhang   Zhang Watson, 1994  
Melt density    f(T, P, X?)   Zhang Ochs and Lange, 1998  
Pressure  200 Mpa until sonic or 1 bar at vent   X Massol    
Rheology    f(T, X, strain rate) X Dingwell Giordano and Dingwell, 2002  
Magma rheology     X   Llewellin et al., 2002 Use capillary number
Bubble number density 1011 m-3       Mangan and Cashman, 1996  
Nucleation  None   X Gardner     
Coalescence  None   X Larsen     
Bubble size distribution Monodisperse   X Mangan    
Fragmentation threshold   me=S=25 MPa X Navon    
Post fragmentation particle size 200 micron   X Bergantz    
Surface tension     X Dingwell Walker, 1979  
Geometry (vent, conduit, chamber) Cylindrical;
50 m diameter;
8 km base		   X Mitchell, Gaffney   Also do fissure geometry- 10 m width. Flow rate per linear m.
Country rock characteristics Rigid, impermeable,
2551 kg/m3		     Starostin    
Recharge from below Output to maintain steady-state     Bergantz    
Transient     X      
Trigger  None   X Koyaguchi    
Drag coefficients; 2-phase flow parameters Smooth walls, no slip, model at will     Papale    

 

Model Output Protocol
Model

Velocity

Volatile conce.

Magmatic pressure profile f(z)

Temperature

Non-equilibrium

Bubble pressure

2-phase flow

Transient

Vesicularity
Proussevitch

x

x

x

x

x

x

  

x

x
Massol

x

x

x

  

x

x

    

x
Starostin

x

x

x

    

x

x

x

x
Bergantz

x

x

x

x

x

  

x

x

x
Tak

x

x

x

x

x

x

x

x

x
Rauenzahn

x

x

x

x

x

  

x

x

x
Mastin

x

x

x

x

        

x
Mitchell

x

x

x

x

  

x

x

  

x
Papale

x

x

x

      

x

  

x
Neri

x

x

x

          

x

Base comparison- v & mass flux, dissolved conc, P, vesicularity, fragmentation conditions.
Tier 1- T, bubble pressure, 2-phase flow (with slip velocity).
Tier 2- transient (w/animations), non-equilibrium, turbulent flow and bubble growth.

 

Send mail to alex.proussevitch@unh.edu with questions or comments about this web site.
Last modified: Tuesday May 08, 2007