Mechanisms

         Explosive vesiculation --The explosion of overpressured gas bubbles in magma, in response to changing conditions associated with the rise of magma from depth. 

readings:

Sparks, R. S. J., 1978, The Dynamics of Bubble Formation and Growth in Magmas: A Review and Analysis: Journal of Volcanology and Geothermal Research, v. 3, p. 1-37.

Dingwell, DB, 2001, Magma degassing and fragmentation, in From Magma to Tephra, ed by A Freundt and M Rosi Elsevier:Amsterdam

Parfitt, EA and L Wilson, 2008, Fundamentals of Physical Volcanology, Ch 5 Volatiles, Blackwell, Malden MA USA

           Fuel coolant (hydrovolcanic) -- Explosions associated with magma/water contact and energetic steam formation.

readings:

Wohletz KH, 1983, Mechanisms of hydrovolcanic pyroclast formation: size, scanning electron microscopy, and experimental studies. In: Explosive Volcanism (MF Sheridan and F Barberi, Eds) Journal of Volcanology and Geothermal Research 17: 31-63.

           Milling or comminution -- Abrasion of ash in pyroclastic flows and on conduit walls.

reading:

Dartevelle S et al, 2002, Origin of the Mount Pinatubo climactic eruption cloud:Implications for volcanic hazards and atmospheric impacts, Geology v. 30; no. 7; p. 663–666

Rosin-Rammler and Weibull distributions:

http://en.wikipedia.org/wiki/Weibull_distribution

http://www.coal.sgs.com/rosin-rammler-particle-size-distribution.htm

http://www.erpt.org/014Q/Nelsa-06.htm

  Components of ash

        Magmatic:  Glass, crystals, phenocrysts, microcrysts, groundmass/microcrystalline material

        Lithic: Phreatic, accidental, conduit walls, others