Physical Sciences and Mathematics Commons^™

The Role Of Fire In Montane Forest Environments In The Willamette National Forest, Oregon, Tamara G. Cox

All Master's Theses

High-resolution charcoal and pollen analyses were used to reconstruct a 16,000-year-long fire and vegetation history of the Blair Lake watershed in the Willamette National Forest of Oregon. The record shows that during the late glacial period, overall fire frequency was relatively low. Pinus and Abies were the dominant vegetation, along with Pseudotsuga and Alnus, suggesting that an open-canopy conifer forest developed soon after the area was glacier free. Fire frequency increased during the early Holocene. Warmer and drier conditions are reflected in the herbaceous vegetation, Artemisia, Poaceae, and Cyperaceae, suggesting that meadows or other openings were part of …

Lidar Assessment Of Sediment Transport Related To The Removal Of The Marmot Dam, Sandy River, Oregon, Carl Daniel Matzek

All Master's Theses

Four Aerial LiDAR survey were used to examine the impacts of the 2007 removal of the Marmot Dam on the Sandy River, Oregon. Geomorphic Change Detection software was used to answer three project goals: 1) to investigate how the dam removal affected sediment distribution in the lower reach of the river, several km downstream of the dam, 2) to determine whether the pulse of sediment from the dam removal created a detectable, successive downstream accumulation of sediment through time, and 3) to assess the effect of natural high-flow events on the sediment distribution related to the dam removal. The results …

Characterization Of Mass Wasting Through The Spectral Analysis Of Lidar Imagery: Owyhee River, Southeastern Oregon, Christopher Earl Markley

All Master's Theses

Quantifying landslide character is an important aspect of understanding hillslope-channel interactions. Spectral analysis of high-resolution, LiDAR derived, DEMs was carried out following methods described by Booth et al. (2009) to determine the characteristic spectral signature inherent in different styles of landslides in the Owyhee River Canyon in southeastern Oregon. The main factor in landslide generation in this location is a lithologic contact in which a coherent basaltic caprock overlies relatively weak sediments where most of the landslide failure surfaces originated. Changes in spectral power distribution through time were quantified by comparing a sequence of adjacent rotational landslides of apparent different …

Petrogenetic Relationship Of The Postcaldera Eruptions Of Mount Mazama, Crater Lake, Oregon; Evolution Of A Sub-Volcanic Magma Chamber Following A Large Silicic Eruption, Michelle Leanna Tebbe

All Master's Theses

Mount Mazama is the volcanic edifice that cataclysmically erupted ~503 km of relatively homogeneous rhyodacite lava ~ 7,700 years ago, forming the caldera known as Crater Lake. Within a few hundred years, andesitic eruptions built three distinct volcanic edifices on the floor of Crater Lake; ~ 3000 years later, rhyodacite eruptions formed a dome (Bacon et al., 2002). How magmatic systems evolve following a shallow, relatively large silicic eruption is the focus of this study. In situ geochemical analysis coupled with high-resolution textural images of plagioclase crystals in the four postcaldera volcanic edifices were used to identify distinct crystal populations …

Lacustrine Sediment Record Of Multiple Quaternary Lava Dams On The Owyhee River, Southeastern Oregon, Caitlin Anne Orem

All Master's Theses

Multiple lava dams and correlating lakes impacted the Quaternary evolution of the Owyhee River. Sediment records from lava-dammed lakes were investigated to understand effects of the West Crater (WC) lava dam (~70 ka), the Saddle Butte 2 lava dam (~144 ka), and the Bogus Rim lava dam (~1.9 Ma). Evidence from the WC lava dam and related features indicates that dam duration consisted of five stages (1) dam and lake formation at ~70 ka; (2) dam overflow and lake sedimentation from ~70–46 ka; (3) removal of lava dam and lake termination from ~46 ka to at least 36 ka; (4) …

Petrogenetic Processes Characterizing The Mount Bachelor, Oregon Magmatic System: Open- Versus Closed-System Processes, Sara Elizabeth Johnson

All Master's Theses

Mount Bachelor volcanic chain (MBVC), located in central Oregon, is one of the larger basalt and basaltic-andesite edifices in central Oregon. Preliminary studies have defined how eruptions have changed composition with time, but a detailed assessment of magma chamber processes has not been conducted. To gain a more thorough understanding of the magmatic processes that have contributed to the observed compositional evolution, this study focuses on one of four eruptive episodes, specifically episode III, the most voluminous episode of the four. Magmatic processes are assessed by focusing on both whole-rock and single crystal data.

The geochemistry and textural diversity of …

Comparison Of Landslides And Their Related Outburst Flood Deposits, Owyhee River, Southeastern Oregon, Shannon Marian Othus

All Master's Theses

Numerous landslides have entered the Owyhee River canyon north of Rome, Oregon. As the river flows through different lithologic units, the style of mass wasting changes from large slump events and small rock falls to large earthflows. The change in mechanism of mass wasting from upstream to downstream seems to depend on several factors: (1) the ratio of the basalt cap to the exposed underlying sediments, (2) the composition of underlying sediments, (3) the canyon geometry, and (4) the extent and frequency of mass wasting. All three mechanisms of mass wasting have the ability to block the river channel and …

Paleoflood Record Reconstruction At An Archaeological Site On The Owyhee River, Southeastern Oregon, Stephanie Louise Vandal

All Master's Theses

The magnitude and frequency of late Holocene floods on the Owyhee River in southeastern Oregon were reconstructed from fine-grained flood deposits at three sites in the river canyon. The stratigraphy at the Birch Creek study site (BCSS) preserves a record of seven to nine large floods from the last 2800 years. Two additional study sites, the Iron Gate and Waterwheel, within a 5-km reach of the BCSS, showed 18-26 floods from the late Holocene to 1993 A.D. and 17-22 floods from 8600 B.P. to 1993 A.D., respectively. Hydrologic Engineering Center-River Analysis System modeling of the 1993 flood and several paleofloods …

Fluvial Response To Intra-Canyon Lava Flows, Owyhee River, Southeastern Oregon, Cooper Cooke Brossy

All Master's Theses

At least six lava flows have entered the Owyhee River Canyon north of Rome, Oregon, since the Pliocene and directly impacted the Owyhee River. The effects on the river of the two youngest lava flows, the West Crater (60–80 ka) and Saddle Butte (> 60–90 ka), are readily apparent. These two lava flows entered a paleo-Owyhee Canyon several kilometers wide via three different tributary drainages. The flows dammed the Owyhee River, created lakes, and effectively confined the river to the opposite side of the valley from the flows’ entrance. Lava from these flows filled a paleo-Owyhee Canyon to depths of …

A Large Late Pleistocene Outburst Flood From Pluvial Lakes Alvord And Coyote Into The Owyhee River, Oregon, Deron Torrey Carter

All Master's Theses

A large late-Pleistocene flood traveled into the Owyhee River as a result of a rise and subsequent outburst from pluvial Lake Alvord in southeastern Oregon. Lake Alvord breached Big Sand Gap after reaching an elevation of 1292 m, releasing 11.3 km3 into the adjacent Coyote Basin before stabilizing at an elevation of about 1280 m. Overflow then spilled out of the Coyote Basin through two outlets at 1278 m and into the Crooked Creek drainage of the Owyhee River. The flood created a series of deeply incised canyons, scabland topography and deposited numerous boulder bars containing imbricated clasts up to …

A Small Look At The Big Picture: Linking Geopotential Height Anomalies To Paleofloods On The Snake River, Idaho And Oregon, Gwendolyn Bernitha Rhodes

All Master's Theses

A combined paleoflood and flood hydroclimatology study on the Snake River in Idaho and Oregon suggests a link between floods and patters of geopotential height anomalies over the North Pacific Ocean. Examination of the paleoflood record in two 4-m (12 ft) tall terraces along the Hells Canyon reach of the Snake River in Idaho and Oregon shows evidence of at least twenty-two late-Holocene extreme floods that occurred approximately 5,000 years. The ages of paleoflood deposits at these sites fall into two time periods, from 5130 ± 40 to 1960 ± 40 yr BP and from 320 ± 40 yr BP …