• VOLCANIC PARTICLES-火山喷发颗粒

  • from ERUPTION of MOUNT ST. HELENS--MAY 18, 1980

ROGER J. CHENG, ASRC UNIVERSITY at ALBANY SUNY

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郑均华 研究员   纽约州立大学 大气科学研究中心

POWER PLANT EMISSION
ACID RAIN FORMATION
ECOLOGICAL EFFECT
ALBEDO of CLOUDS
BUILDING EROSION
ATMOSPHERIC PTS
CARBONACEOUS PTS
AIR POLLUTION CONTROL
  • The MECHANISMS of FINE PARTICLES GENERATION and
  • ELECTRIFICATION During MOUNT ST. HELENS VOLCANIC ERUPTION

ROGER J. CHENG-UALBANY

ASRC UNIVERSITY at ALBANY SUNY

ABSTRACT

Microscopically Investigation of volcanic ash collected from ground stations during Mount St. Helens eruptions reveal a distinctive bimodal size distribution with high concentrations of particle ranges at (1) 200- 100 um and (2) 20-0.1 um, respectively. Close examination of individual particles show that larger ones are solidified magma particles of porous pumice with numerous gas bubbles at its interior, and that the smaller ones are all glassy fragments without any detectable gas bubbles. Very few of the fragments are below 0.1 um and no evidence could be found indicating that the small particles are formed by the condensation process.

Elemental analysis demonstrates that the fine fragments all have a composition similar to those of the larger pumice particles. Laboratory experiments suggest that the formation of the fine fragments is by bursting of glassy bubbles from a partially solidified surface of a crystallizing molten magma particle. The production of gas bubbles is due to releasing absorbed gases in molten magma particles when solubility decreases, during phase transition. Diffusion cloud chamber experiments strongly indicate that sub-micron volcanic fragments are highly hygroscopical and extremely active as cloud condensation nuclei. Ice crystals also are evidently formed on those fragments in a super cooled (-20C) cloud chamber. It has been reported that charge generation from ocean volcanic eruptions is due to contact of molten lava with sea water. This seems insufficient to explain the observed rapid and intense lightning activities over Mount St. Helens eruptions.

A hypothesis is, therefore, presented here that highly electric charged fine solid fragments are ejected by bursting of gas bubbles from the surface of a crystallizing molten magma particle. The charge separation process by thermal electric effect is taking place within this crystallizing particle, and their polarities are determined by temperature gradient between the colder surface of the solid glassy bubbles and Interior of the particle with a much higher temperature. After bursting, positively charged fine fragments are ejected and carried by convection to the top of a volcanic plume and negatively charged and heavier solidified plumic particles gradually fall by gravity to the base of the plume, and eventually reach the ground.

It is suggested that the fragmentation of volcanic ash and its accompanying electrification may play an important role in the generation of electric fields which may become strong enough to initiate lightning during volcanic eruption, and also have definite impact on climatological effects in the atmosphere.

  • Presented at Symposium on Mount St. Helens Eruption:
  • Its Atmospheric Effects and Potential Climatic Impact.
  • Sponsored by NASA-Office of Space and Terrestrial Applications,
  • November 18-19, 1980, Washington, D.C

 

The AIR SAMPLES of VOLCANIC ASH WERE COLLECTED

on THE DAY of MAY 20. 1980 and ANALYZED

at ASRC'S WHITEFACE MT. FIELD RESEARCH STATION

http://rogerjcheng.com/ENVIRONMENT-ATMOSPHERIC%20PARTICLES.htm

http://rogerjcheng.com/The%20MICRO-WORLD%20in%20the%20THUNDERSTORM.htm

http://rogerjcheng.com/The%20MICRO-WORLD%20in%20OUR%20ENVIRONMENT.htm