In November, 2006, a storm generated a minimum of 34 cm of precipitation in six days, triggering debris flows in many of the drainages on all sides of Mount Hood, Oregon. Of the eleven drainages surveyed, seven experienced debris flows; these include the White River, Salmon River, Clark Creek, Newton Creek, Eliot Creek, Ladd Creek and Sandy River basins. Flows in the White River, Eliot Creek, and Newton Creek, caused major damage to bridges and roadways. Initiation elevations averaged around 1,860 meters. Initiation zone material was predominantly sand (45-82%) with gravel (15-49%) and had few fines (3-5%). Four debris flows were triggered by landslides caused by undercutting of the river banks. Three developed through coalescence of multiple small debris flows within major channels and were termed "headless debris flows". Physical and morphological characterization of source areas was used to assess factors controlling debris flow initiation. Although findings indicate that all major drainages on Mount Hood are capable of producing debris flows, drainages with direct connection to a glacier, low percentages of vegetation, and moderate gradients in the upper basin were the most susceptible. Among basins not having debris flows, neither the Zigzag River nor Polallie Creek have a direct connection to a glacier, And the Muddy Fork and the Coe both have high percentages of vegetated slopes. The material in the upper basin of the Muddy Fork is predominately rock making initiation there weathering-limited. Additionally, the Muddy Fork and the Zigzag have two of the steepest gradients on the mountain. This pattern suggests that material there is regularly transported downstream through normal fluvial processes rather than building up to be catastrophically removed through debris flow processes.

Throughout its eruptive history, Mount Hood has produced compositionally similar calc-alkaline andesite as lava flows and domes near the summit and basaltic andesitic flows from flank vents. Found within the andesite are slightly more mafic inclusions that are compositionally similar to the host andesite (or host lavas); no inclusions were found in the flank lavas. Host lavas and inclusions have the following mineral assemblage: plag + opx ± cpx ± amp + oxides. Flank lava mineralogy is similar to the inclusions and host lavas, but since they are more mafic they contain olivine instead of amphibole. Average silica content among samples analyzed ranges from 57.6 to 62.7 weight percent; however the incompatible trace element composition is more variable at lower silica contents and becomes less variable at higher silica contents. In terms of incompatible trace element composition, the host lavas and inclusions are either depleted (no amp) or enriched (amp± cpx).

Observations or a small group of pikas, (Ochotona princeps) occupying a southwest facing roadfill on Mt. Hood, Oregon (1518 m) were made during the fall or 1976. Territorial sizes of 305.5 m2 and 121 m2 were determined based on territorial displays. These territories were compared with those observed in other studies. The mean distance to the nearest neighbor was 15.1 m. A pair relationship between two of the pikas and a dominance order are discussed. The seasonal progression of the haypiles and the reactions of the pikas to other animals are also noted.

Ten mountain lakes were analyzed in order that they be assigned a trophic status. The lakes which are located in the Mount Hood National Forest of Oregon are Anvil, Beaver Pond, Cripple Creek, Fish, Gifford, Monon, Ollalie, Rimrock, Round, and Sportsman. The purpose of this report is to determine the productivity of these waters. Data were collected for analyses of temperature, dissolved oxygen concentration, Secchi depth, major ion concentration, light intensity versus depth, alkalinity, phytoplanktcn species composition/total density, and zooplankton species composition/total density. Samples were collected in Van Darn sampling bottles and returned to the laboratory for chemical analyses and taxonomic identification of biological organisms. Field profiles were taken for light intensity, temperature, dissolved oxygen concentration, specific conductivity, and depth using portable electronic equipment. A Secchi disk was used in the field for obtaining light extinction data. The lakes were assigned a trophic status according to carlson's Trophic State Index (Carlson, 1977). Beaver Pond Lake which is the most productive lake of the 10 surveyed had an average Secchi depth of 1.7 meters, an average soluble reactive phosphorous concentration of 59.8 ug/L, and an average chlorophyll-a concentration of 29.3 ug/L for the dates sampled. These values are consistent with lakes which are eutrophic. Ollalie Lake had an average Secchi depth of 13.2 meters, an average soluble reactive phosphorous concentration of 1.64 ug/L, and an average chlorophyll-a concentration of 0.28 ugfL. This lake is ultraoligotrophic-to-oligotrophic according to the Carlson index. The other lakes of the study were assigned values for trophic state which are somewhere between those assigned to Beaver Pond and Ollalie lakes. The 10 lakes studied for this report were compared to lakes studied for the compilation of the Western Lake survey (Landers, et. al. 1987). It was noted that Beaver Pond, Round, and Sportsman lakes are nutrient rich while Monon, Ollalie, and Gifford, are nutrient poor when compared to other lakes located in the Pacific Northwest. Anvil, Cripple Creek, Fish, and Rimrock lakes have profiles consistent with the majority of mountain lakes located in the area.

Mount Hood is an Oregon icon. The mountain has as long and rich a history of recreation and tourism as almost any other place in the American West. But contemporary landscapes on Mount Hood reveal a recreation and tourism industry that has struggled to assert itself, and a distinct geographic divide is evident in the manner in which tourism has been developed. Why? In this study I chronicle the historical geography of recreation and tourism on Mount Hood. I examine the evolution of its character and pattern, and the ways in which various communities have used it to invest meaning in the places they call home. Despite the efforts of early boosters, Mount Hood has never been home to an elite destination resort like Aspen, Sun Valley, or Vail. Instead, modest recreation developed alongside timber and agriculture, and today the area is primarily a regional attraction. Unlike destinations with national and international clienteles that play a significant role in shaping lives and landscapes, local and regional interests are the primary drivers of recreation and tourism on Mount Hood. Communities on the mountain have incorporated the industry into their lives and landscapes to varying degrees. Mount Hood is also inextricably tied to Portland, and as an integral part of the city's history and identity, reflects its residents' tastes, values, and priorities. This combination of local and metropolitan interests has left an imprint on Mount Hood that reflects tensions and contradictions that define Oregon in the early twenty-first century: past vs. future, old vs. new economies, urban vs. rural inclinations, progress vs. status quo, and upscale vs. modest tastes. Spatially, temporally, and psychologically, Mount Hood straddles the divide between two visions: a service-based economy in the Willamette Valley, heavily dependent on technology, and a traditional, resource-based economy in much of the rest of the state.

Soils from two active earthflows, two earthflow deposits, and three non-earthflow landforms are examined to determine if a connection exists between near-surface soil properties and rates of earthflow movement. The study area is located in the Clackamas Ranger District of the Mt. Hood National Forest in the northern Oregon Cascades. Its geology consists of clay-bearing volcaniclastic formations overlain by unaltered flows of andesite and basalt, a combination that contributed to large-scale landsliding during the late Pleistocene. Deposits from these landslides now cover much of the valley floor, and it is from these deposits that earthflows tend to mobilize. The main hypothesis is that near-surface soil properties reflect earthflow movement and may be used to distinguish between active and inactive earthflows. The results support this hypothesis and indicate that soils in each of the three categories show clear differences in terms of their physical properties. The mean field moisture content of active earthflows is 56 percent, while that of earthflow deposits is 46 percent and that of non-earthflow landforms is 36 percent. All samples from active earthflows exhibit plasticity, whereas 90 percent of samples from earthflow deposits and only 25 percent of samples from nonearthflow landforms exhibit plasticity. The mean liquid limit of active earthflows is 78 percent, compared to 60 percent for earthflow deposits and 46 percent for non-earthflow landforms. The mean plasticity index of active earthflows is 41 percent, compared to only 13 percent for earthflow deposits and non-earthflow landforms. These differences are largely attributed to clay content and clay type. The mean clay content of active earthflows is 46 percent, compared to 24 percent for earthflow deposits and only 5 percent for nonearthflow landforms. In contrast, the mean sand content of active earthflows is 20 percent, while earthflow deposits contain 40 percent and non-earthflow landforms 50 percent. This difference in particle sizes is reflected in friction angle. Active earthflows have a mean friction angle of 15 degrees, compared to 24 degrees for earthflow deposits and 31 degrees for non-earthflow landforms. These results indicate that soil properties can be used to draw distinctions between active and inactive earthflows. However, soil properties are much less effective at distinguishing between active earthflows that move at different rates. For example, Junction earthflow, which moves only a few centimeters per year, is composed of soils that indicate it to be less stable than the Collowash earthflow, which moves approximately 2 meters per year. The reason for this discrepancy is that, in addition to soil properties, the rate of earthflow movement depends on the complimentary effects of hydrology, slope angle, toe erosion, and boundary roughness. Many ancient landslide deposits in the Mt. Hood National Forest are poised for action and may mobilize upon the slightest provocation. Since this is not seen as a "desired future condition" there is a need to differentiate between those deposits with a potential for reactivation and those likely to remain dormant. Examining the physical properties of soils appears to be one way to do this, and the information collected is valuable to land managers and earth scientists alike.

Magma recharge events and subsequent mixing processes are understood to precede volcanic eruptions. Textural evidence of intrusion of hot, mafic magma into a cooler, rheologically locked silicic magma is commonplace. Solidified "blobs" of injected magma, called enclaves, are evidence of magma mixing, but the petrological and mechanical conditions during their formation are debated. Mount Hood, Oregon consistently erupts andesite bearing compositionally similar enclaves. These enclaves are evidence of mingling and mixing of two magmas. However, due to the compositional similarity between enclave and host lava (e.g. ~1-5 wt.% difference in SiO2), it is unclear whether the preserved enclaves represent; 1) partially hybridized mafic melt remaining after mixing with significant crystal exchange with the host magma or 2) the preserved remnants of the intruding magma during recharge, with no homogenization or crystal exchange with the host magma. The aim of this study is to understand how and why enclaves form in compositionally similar host magmas, such as those at Mount Hood. Building off previous research, we utilize a combination of field observations, chemical analyses, and numerical modeling to constrain the rheology of the magmas prior to and during mixing. The degree of magma mixing is dependent on the viscosity contrast between the host and intruding magmas. Since these magmas are similar compositionally, variations in other magmatic properties such as crystallinity, and therefore temperature, and density may drive the viscosity differences between the host and intruding magmas needed for enclave formation. The enclaves at Mount Hood are vesicular (13-28%), coarse-grained; made up of mainly groundmass crystals (200-450 µm) with sparse microlites (< 200 µm), glass (450 µm) proportions, and rarely contain quenched margins. Additionally, crystals within the host magma show preferential alignment along the margins between host and enclave, suggesting a fluid behavior of the host magma during mixing. Based on textural and compositional evidence, we hypothesize that the intruding magma was buoyant, viscous, and crystalline, due to decompression-induced crystallization and exsolution of volatiles, during recharge and ascent to the shallow magma reservoir. Injection and underplating of the viscous crystalline intruding magma into a hot convecting host magma induces enclave formation. Crystallization temperatures differ by only 6-15 °C between host and enclave lavas, derived by the two pyroxene geothermometry method by Putrika (2008). These crystallization temperatures are consistent with crystallization in compositionally similar magmas. However, with such similar crystallization and liquidus temperatures, maintaining a viscosity contrast between the mixing magmas for enclave survival after formation suggests other properties, apart from temperature, must explain the viscosity contrast needed for enclave survival after enclave dispersal and thermal equilibration occurs. The presence of bubbles, from exsolution during crystallization, within the enclave magma increases the viscosity while simultaneously decreasing the density. Therefore, the presence of bubbles increases the viscosity of the intruding magma and maintains the viscosity contrast during the mixing process after thermal equilibration occurs. Additionally, if degassing occurs, rapid crystallization maintains the high viscosity of the enclaves. The enclaves observed at Mount Hood represent the solidified remnants of the last recharge event prior to eruption. The presence of compositionally similar enclaves and host lavas suggest a transient precursor event just prior to eruption at Mount Hood and can be applied to other recharge-driven arc volcanic systems.

Over a span of six days from November 2-7, 2006 approximately 43 cm of precipitation fell over the Hood River Basin in Oregon. A lahar was initiated on the Eliot Branch of the Middle Fork Hood River by two or more landslides that occurred on the lateral moraines of the Eliot Glacier on the early part of November 7th, 2006. The Eliot Branch lahar was embedded within the larger regional flood that was occurring in the Hood River Basin and traveled a total of 48 km from the initiation points on the north flank of Mount Hood to the Hood Rivers confluence with the Columbia River. The initiating landslides abruptly transformed into a debris flow upon mixing with flood waters of the Eliot Branch. The debris flow traveled a distance of ~28 km at which point it was transformed first to a hyperconcentrated flow and then to water flow via selective deposition of coarse sediment and progressive dilution by channel flow waters from the East and West Fork Hood Rivers. The transformation from debris flow to hyperconcentrated streamflow was recorded by a thickening wedge of hyperconcentrated streamflow sediments found above and below progressively fining debris flow sediments over a reach of 22 km. Finally, the hyperconcentrated-flow phase of the lahar transformed to water flow and then traveled an additional 20 km to the Hood River delta. Upon reaching the apex of the Hood River delta, depositing sediments led to an expansion of the delta. Debris-flow sediments were predominantly gravel (36.0-69.7% by wt.) with sand (22.1-55.9% by wt.) and fines (4.7-7.8% by wt.). Hyperconcentrated flow deposits contained a larger sand fraction of (66.8-99.2% by wt.) with few gravel clasts (0-26.0% by wt.) and fines (0-8.8% by wt.). Water flow deposits averaged 90.5% (wt.) sand with 6.0% (wt.) gravel and 3.0% (wt.) fines. Sorting was a key factor in flow identification and showed progressive improvement downstream from the initiation point. Sorting values for the flow types are as follows: debris flow deposits ranged from 3.3Φ (very poorly sorted) to 1.8Φ (poorly sorted), hyperconcentrated flow deposits ranged from 2.4Φ (very poorly sorted) to 0.8Φ (moderately sorted), and water flood deposits ranged between 1.4Φ (poorly sorted) to 0.6Φ (moderately sorted).

The Miocene Rhododendron and Dalles Formations in the Mount Hood area are accumulations of chiefly pyroclastic andesitic material, largely confined to the Dalles-Mount Hood syncline. These very similar units are geographically separated by overlying andesites including the present Mount Hood cone, and past workers (Hodge 1938, Wise 1969) have suspected that they may share a common source. Prior to this study, few geochemical data were available for the Rhododendron and the Dalles Formations, compared to the well studied Columbia River basalts underlying them and the overlying Pliocene andesites. This geochemical study was designed to investigate certain aspects of the Rhododendron and Dalles Formations such as their possible common source, how they differ chemically from other andesites in the area, and how they fit into the chemical evolution of the Cascade Mountains.

During the past fifteen years, non-timber or special forest products have become an important economic resource in the Pacific Northwest. These products are primarily derived from understory species and contribute approximately $200 million to the regional economy. Medicinal plants are a little researched component of the non-timber forest product industry that relies on cultivated and wildcrafted (or wild-collected) medicinal plant species. This study examines the commercial extraction of wildcrafted medicinal plants from Mount Hood National Forest. Specifically, this study documents the medicinal plant species extracted from Mount Hood National Forest, their annual yield amounts, harvesting methods, and the changes in cover of target species after harvest. This research uses survey data obtained from employees of two herbal companies and representatives of the U.S. Forest Service to describe medicinal plant extraction and administration as it pertains to the commercial extraction of plant species from Mount Hood National Forest. Field data were also used to examine changes in plant cover for four medicinal plant species (kinnikinnick, yarrow, Oregon grape and valerian) following harvest. Field results indicate that medicinal plant cover decreased significantly in all but one harvested sampling unit. Permanent unit markers were established at all the study sites to provide opportunities for long-term monitoring of target species responses to harvest. Eleven medicinal plant species are commonly collected for commercial purposes from Mount Hood National Forest. The general lack of regulation and enforcement of commercial medicinal plant extraction coupled with an increasing demand for wildcrafted medicinal plants warrant a need for increased collaboration between regulatory agencies, herbal companies, and the general public. Additional management and research recommendations regarding the ecological impacts of medicinal plant removal are also presented.