About 7,000 years ago two major tephra-falls blanketed the
Pacific Northwest in volcanic ash. These two tephra-falls, identified
as the Llao and climatic tephra-falls, were a part of the eruptive
events that led up to the collapse of Mount Mazama to form Crater Lake
in the southern Oregon Cascades.
The...
Field and laboratory studies were conducted on volcanic ash from Yakima, Moses Lake, Spokane, Washington, and Moscow, Idaho, three weeks after the May 18, 1980, eruption of Mt. St. Helens in southwestern Washington. These studies examined 1) the chemical, physical, and water retentivity properties of the ash, 2) the effect...
Soils developed on volcanic ash exhibit several unique properties
not commonly observed in soils formed on other geologic
material. Low thermal conductivities, low volumetric heat capacities,
slow transport phenomena, excess macro-drainage and
development of unique suites of clay minerals are some properties
thought to be directly related to the vesicular...
This study was undertaken in a Red Delicious apple orchard in
Oregon's Hood River Valley to determine if low leaf P concentrations
were contributing to such observed, orchard disorders as poor shoot
growth, shoot dieback and. small fruit size at harvest.
Subsurface applications of lime and superphosphate had no
effect...
The basement of the Tonga intraoceanic forearc comprises Eocene arc volcanic crust formed during the earliest phases of subduction. Volcanic rocks recovered from the forearc include boninites and arc tholeiites, apparently erupted into and upon older mid-oceanic ridge tholeiites. Rock assemblages suggest that the forearc basement is a likely analog...
The Bend pumice and Tumalo tuff are products of a plinian eruption which occurred sometime between 0.89 and 2.6 m.y. The Bend pumice is a poorly consolidated, air-fall vitric lapilli tuff, which overlies a zone of reworked tephra. Perlitic obsidian in the reworked zone probably represents the remains of a...