Mt. St. Helens

Fig. 6-1. Mt. St. Helens during the eruption of May 1980. Source Photo by C. Rosenfeld, Oregon Air National Guard.

It should be noted that, even when good U-Th mineral isochrons indicate old crystallization ages, Ra- Th disequilibria can be found in minerals, groundmass and whole rocks. It is the case for Mt. St Helens and Mt. Shasta (Volpe et al. 1991, 1992) and Vesuvius (Black et al. 1998) (see Fig. 10c,d) this requires either a selective Ra enrichment in the magma shortly before eruption accompanied by further crystallization... 

Villemant B, Boudon G, Komorowski JC (1996) U-series disequilibrium in arc magmas induced by water-magma interaction. Earth Planet Sci Lett 140 259-267 Volpe AM, Hammond PE (1991) U- °Th- Ra disequilibrium in young Mt. St. Helens rocks time constraint for magma formation and crystallization. Earth Planet Sci Lett 107 475-486 Volpe A M (1992) U- °Th- Ra disequilibrium in young Mt. Shasta andesites and dacites. J Volcanol Geotherm Res 53 227-238... 

Oe 0.8-2.8 cm partially decayed needles and twigs Oa 2.8-33 cm well decayed OM/Mt. St. Helens volcanic ash A 3.3-12.7 cm pale brown (10YR 6/3) gravelly ashy silt loam, very fine granularstructure... 

Salaymeh S, Kuroda PK. 1987. Variation of the thorium to uranium ratio in rain Thorium-230 chronology of the eruptions of Mt. St. Helens and El Chichon volcanoes. J Radioanal NucI Chem 116 261-269. 

FIGURE 8 Change in phenolic hydroxyl content of fulvic acids from Spirit Lake during the several years after the eruption of Mt. St. Helens (from McKnight et al., 1988). The measurement of phenolic hydroxyl content is by derivitization with 13C-enriched diazomethane that is quantitatively measured by 13C-NMR spectroscopy. 

Deepak a. ed.. Atmospheric effects and potential climatic impact of the 1980 eruptions of Mt. St Helens. NASA Conf. Publ. 2240, 1982. 

Evans W.F.J. and Kerr J.B., Estimates of the amount of sulphur dioxide infected into the stratosphere by the explosive volcanic eruptions El Chichon, mystery volcano, Mt. St. Helens. Geophys. Res. Lett., 10, 1049-1051 (1983). 

McGee K. A. (1992) The structure, dynamics and chemical composition of non-eruptive plumes from Mt. St. Helens, 1980-88. J. Volcanol. Geotherm. Res. 51, 269-282. 

Plagioclase microlite size distributions have been attributed to largely syn-eruptive crystallization, as illustrated by the rhyolitic groundmasses of Merapi (Hammer et al., 2000), Mt. St. Helens (Cashman, 1992 Geschwind and Rutherford, 1995), and Pinatubo (Hammer et al.,... 

Cooper K. M. and Reid M. R. (2003) Re-examination of crystal in recent ages. Mt. St. Helens lavas. Earth. Planet. Set Lett. 213, 149-167. 

There are numerous calculations of the multi-component chemical equilibria in gas-solid-liquid systems within volcanoes (e.g., for Mt. St. Helens see Symonds and Reed, 1993). These typically show the importance of SO2 at high temperatures (see Figure 8) and a transition to a dominance of H2S at lower temperatures in systems such as... 

Figure 8 Multicomponent chemical equilibria in gas-solid-liquid systems within Mt. St. Helens (source Symonds and Reed, 1993).

Perry, R.W. Lindell, M.K. Living with Mt. St. Helens Human Adjustment to Volcano Hazards Washington State University Press Pullman, WA, 1990. 

Lakes of Mt. St. Helens Region South Fork Castle ... 

Relative to soil humic substances, humic substances from Lake Celyn, Wales, and fulvic acids from lakes near Mt. St. Helens contain larger amounts of reactive acidic functional groups (especially carboxyl groups). The reason for this is not known. In Lake Celyn, 24% of the humic acid carbon is carboxyl and 40% is aromatic, suggesting that the Lake Celyn humic acids are largely of terrestrial origin (M. A. Wilson et al., 1981a). 

McKnight, D. M., Periera, W. E., Zeazan, C. L., and Wissmar, R. C. (1982). Characterization of dissolved organic materials in surface waters within the blast zone of Mt. St. Helens, Washington. Org. Geochem. 4, 85-92. 

Hoffmann, D.J., and J.M. Rosen, Balloon-borne Observations of Stratospheric Aerosol and Condensation Nuclei During the Year Following the Mt. St. Helens Eruption. University of Wyoming Report AP-63, 1981. 

It is estimated that the day Mt. St. Helens erupted (May 18, 1980), about 4.0 X 10 tons of SO2 were released into the atmosphere. If all the SO2 were eventually converted to sulfuric acid, how many tons of H2SO4 were produced ... 

Particulates in the atmosphere can cool Earth by scattering and partially reflecting light from the Sun. Large volcanic eruptions such as those from Mt. St. Helens in 1980 and Mt. Pinatubo in 1991 had measurable cooling effects on Earth. 

Major contributors to the amount of atmospheric particulates were volcanic eruptions by Krakatoa, Indonesia, 1883 Mt. Katmai, Alaska, 1912 Hekla, lee-land, 1947 Mt. Spurr, Alaska, 1953 Bezymyannaya, U.S.S.R., 1956 Mt. St. Helens, Washington, 1980 and Mt. Pinatubo, 1991. 

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