In a subduction zone, the volcanic arc marks the location where magma, generated via flux melting in the mantle wedge, migrates through the crust and erupts. While the location of deep magma broadly defines the arc position, here we argue that crustal structures, identified in geophysical data from the Washington...
Since the eruption of Mount St. Helens on May 18,1980, the rural communities within its shadow have experienced tremendous change. Tourism has become a highly visible and somewhat controversial component of change in the region, and its importance to local economies has increased. As a result of increased tourism development...
Riparian vegetation patterns within the blast,
downstream of blast, and airfall tephra zones of Mount
St. Helens are related to initial and secondary volcanic
disturbance, post-eruption fluvial landforms, channel
geometry, and streamflow characteristics. Vegetation
patterns were determined from species presence observed on
transects across landforms developed along the streams.
Distinct...
The 18 May 1980 eruption of Mount St. Helens, emplaced between 3-3.5 billion cubic yards (bcy) of poorly sorted material ranging from silt to boulders, extending from river mile (RM) 25 to RM 38 in the upper North Fork Toutle River drainage. Sediment yields from the debris avalanche were calculated...
The effects of burial by tephra (volcanic aerial ejecta) on
forest understory plants were examined northeast of Mount St. Helens,
Washington, in the area where the 18 May 1980 eruption deposited
tephra but did not destroy canopy trees. At six sites along a tephra
depth gradient from 2-15 cm, understory...
I used satellite remote sensing to examine the key factors controlling the natural revegetation of Mount St. Helens since its eruption in 1980. The study required three stages: determining the amount of vegetation present; characterizing vegetation change; and analyzing the influence of factors affecting vegetation change. To determine the amount...
Comprehension of eruptive histories is critical in understanding the evolution of magmatic systems at arc volcanoes and may supply evidence to the petrogenesis of intermediate and evolved magmas. Within the 300 ka eruptive history of Mount St. Helens, Washington, the Kalama Eruptive Period, 1479- ~1750 CE was bracketed by interludes...
The cultural influence of volcanic eruptions has been emphasized in the archaeological literature. However, the larger effects that Mount St. Helens volcanic eruptions had upon prehistoric populations in the Pacific
Northwest is not understood. This thesis asks questions of the archaeological and paleoenvironmental record of the Pacific Northwest to assess...
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...
The morphology, genesis, and classification of soils
forming in multiple tephra deposits of recent age from
Mt. St. Helens volcano in southwestern Washington Cascade
Mountains was studied.
Soils which occupied well drained and poorly drained
positions on the landscape were characterized according
to their morphology and the results of analyses...
A descriptive model of the routing of sediment that was
delivered to the study area by the 1980 eruptions of Mount St.
Helens has been developed. On hillslopes this sediment was
distributed among three major storage compartments: 1) the tephra
profile, 2) primary storage, and 3) secondary storage. The most...
The 1980 eruptions of Mount St. Helens damaged or destroyed vegetation on more than 66,100 hectares (270,000 acres) within the Gifford Pinchot National Forest. The effects of the eruption on planting sites and seedling performance were unknown. Regeneration of "cut over" lands near Mount St. Helens has historically been limited...
The Mount St. Helens eruption of May 18, 1980, offered an
excellent setting for evaluating early response of ecosystems to
disturbance. Prior to the eruption, the area was densely forested
with fir, hemlock, and Douglas-fir, and various understory species.
During the course of the eruption, hillslopes within a 180 degree...
Information concerning the factors controlling seedling establishment on tephra deposits (airfall volcanic ejecta) is limited. The establishment and growth of six coniferous species, Abies amabills (Dougl.) Forbes (Pacific silver fir), A. procera Rehd. (noble fir), Pinus monticola Dougl. (western white pine), P. Contorta Dougl. (lodgepole pine), Pseudotsuga menziesii (Mirb.) Franco...
The primary goal of this study is to assess the impact of a subduction component
added to the mantle wedge beneath the Oregon Cascades to the composition and fO2 of
primitive Cascade basalts. Olivine-hosted melt inclusions from compositionally diverse
basalts across the Cascade arc (~100 km) are utilized in an...