The objectives of this study are to measure the ash deposition in the field and collect samples of this ash for complete laboratory characterization which includes chemical, physical, mineralogical, elemental and engineering analyses.  The recent ash collected from the forest and undisturbed areas was compared to previous ash depositions in the area and the underlying soil.

The thickness of the ash ranged from 14 mm in the west to <1 mm in the eastern part of the study area.  The thickness of the ash had decreased to 1/2 - 1/5 the original thickness.

The CEC ranged from 1.2-2.6 meq/100 g in undisturbed volcanic ash samples.  NaF pH was <9.4 in the recent ash and >9.4 in the underlying Mazama ash rich soils.  Phosphorous is not sorbed as much in the recent ash as in the underlying Mazama ash.

Particle size distribution, by the Coulter Counter method, averaged 17% sand, 77% silt, and 6% clay on undisturbed samples.  Samples from the forested environments, collected after 5 months of illuviation and reworking, showed that the clay decreased to 1-3%.

Petrographically, the recent ash is similar to Mt. St. Helens set 'T' (1800 A.D.) The refractive index is 1.498-1.502 and the major phenocryst is hypersthene.  X-ray analyses showed the plagioclase is andesine/labradorite and the major clay sized mineral is smectite with minor amounts of vermiculite, an interlayered clay (7-10Å) and cristobalite.

Microprobe data confirms that the recent ash and St. Helens 'T' are similar.  The recent ash and St. Helens 'T' data are:  K=1.6%, Ca=1.7% and Fe=1.8%.  The unweathered Mazama and soil ash data are:  K=2.2%, Ca=1.1%, Fe=1.6%.

Neutron activation analysis shows there are no toxic quantities of elements in the recent ash.  The weathered soil Mazama ash has an increase of Fe and Al over the unweathered Mazama ash, thus creating Bs horizons within the Mazama rich soils.

Hydraulic conductivity, Proctor analysis and particle density data suggest a direct relationship to the amount of clay, organic matter and the mineralogy of the sample.