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Geomorphology

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Articles 31 - 60 of 123

Full-Text Articles in Geomorphology

Quantifying Tekeze River Canyon Incision On The Ethiopian Plateau From Low-Temperature Apatite Thermochronology, Jacob Thomas Grigsby Apr 2020

Quantifying Tekeze River Canyon Incision On The Ethiopian Plateau From Low-Temperature Apatite Thermochronology, Jacob Thomas Grigsby

Masters Theses & Specialist Projects

The Ethiopian Plateau in East Africa features dynamic topography, deep river incision (~1.5 km), active tectonics, continental rifting, volcanic terrain and ~2 km of plateau uplift. Situated on the northwestern part of the Ethiopian Plateau, the Tekeze River is one of the two major rivers associated with incising and documenting the recent geologic history of the uplifted plateau landscape. The consequential Tekeze River incision into the uplifted Ethiopian Plateau is associated with the arrival and impingement of the Afar mantle plume as evidenced by the presence of thick sheets of Cenozoic flood basalts (~30 Ma). However, the Cenozoic to present-day …


Tidal-Groundwater Study Of The Slaughter Beach Salt Marsh In Slaughter Beach, De, Michael Powers Jan 2020

Tidal-Groundwater Study Of The Slaughter Beach Salt Marsh In Slaughter Beach, De, Michael Powers

West Chester University Master’s Theses

Seasonal and decadal monitoring of salt marsh at Slaughter Beach, DE documented long-term and short-term variations in number and sizes of salt ponds. Over 400 salt ponds ranging in size between 0.5 m2 to 0.11 km2 were identified on 5.5 km2 salt marsh platform. The purpose of this study is to quantify hydrologic conditions and measure groundwater discharge of a salt marsh, particularly the impact of tidal forces on groundwater fluctuation.

Four wells with nests of mini-piezometers with ONSET Pressure Transducers were installed along a transect crossing the largest salt pond (0.11 km2) in the …


Late Holocene Paleoflood Hydrology Of The Snake River In The Lower Hells Canyon, Idaho, Kent C. Allen Jan 2020

Late Holocene Paleoflood Hydrology Of The Snake River In The Lower Hells Canyon, Idaho, Kent C. Allen

All Master's Theses

The Snake River watershed spans a large geographic region from the Rocky Mountains to the inland Pacific Northwest, and a comprehensive paleoflood chronology on the mainstem of the river is key to identifying the frequency and magnitude of large prehistoric floods within the region. We examined and compared four sites of slackwater deposits along a 20-km reach of the Lower Hells Canyon on the Snake River, Idaho. The sites contain evidence of up to 34 paleofloods within the last 1700 years. Stratigraphic breaks, soils, and in-situ plant or archaeological materials demarcate distinct layers that represent discrete paleoflood events. Radiocarbon dates …


Distribution Of Invasive Plant Species On Debris Cones At Mount Rainier National Park, Shaun Morrison Jan 2020

Distribution Of Invasive Plant Species On Debris Cones At Mount Rainier National Park, Shaun Morrison

All Master's Theses

Invasive plant populations within Mount Rainier National Park are a biological and ecological threat to the unique mountain landscape. A better understanding of their distribution and transport within the landscape is needed to improve invasive species monitoring for National Park Service management. This study investigates how invasive plant populations in Stevens Canyon are utilizing the debris cone disturbances and associated geomorphic processes to facilitate movement within the park. Vegetation transects were performed along Stevens Canyon Road (to observe the roadside community composition) and on the debris cone features (to observe species movement from the roadside). These vegetation observations are presented …


Geomorphology And Chronology Of Sand Stringer Deposition Beyond The Ice Margin: Southeastern Minnesota And Western Wisconsin, Usa, Richard J. Mataitis Jan 2020

Geomorphology And Chronology Of Sand Stringer Deposition Beyond The Ice Margin: Southeastern Minnesota And Western Wisconsin, Usa, Richard J. Mataitis

All Graduate Theses, Dissertations, and Other Capstone Projects

The purpose of this Master’s thesis is to investigate linear, aeolian deposits termed “sand stringers” located within western Wisconsin and southeastern Minnesota. Previous research has investigated their spatial distribution, and to a minor extent, their composition and absolute age. However, further sedimentological and absolute age data are needed from a greater distribution of sand stringers to understand their formation and depositional chronology. To build on previous research we 1) remotely mapped the spatial distribution and orientation of sand stringers in western Wisconsin and southeastern Minnesota, 2) collected absolute age data using optically stimulated luminescence (OSL) from four stringers in western …


Geomorphic And Land Use Controls On Headwater Channel Morphology In Mark Twain National Forest, Grace F. Roman Aug 2019

Geomorphic And Land Use Controls On Headwater Channel Morphology In Mark Twain National Forest, Grace F. Roman

MSU Graduate Theses

Prescribed burning has been used over the past two decades to manage forests and restore shortleaf pine-oak woodlands in Mark Twain National Forest (MTNF). While soil studies have been completed, no assessments of burning practices on small drainage channel systems have yet been done. Headwater streams may account for more than two-thirds of total stream length and are important to the maintenance of hydrologic connectivity in watersheds. This study’s focus is on understanding the relationship between frequency of forest burning and channel morphology (size, shape, and substrate) of headwater streams (km2). A combination of field measurements, geo-processing methods, …


Distributary Channel Networks As Moving Boundaries: Causes And Morphodynamic Effects, Robert C. Mahon, John B. Shaw, Wun-Tao Ke, Christopher A. Cathcart Jul 2019

Distributary Channel Networks As Moving Boundaries: Causes And Morphodynamic Effects, Robert C. Mahon, John B. Shaw, Wun-Tao Ke, Christopher A. Cathcart

Earth and Environmental Sciences Faculty Publications

We propose an exploratory model to describe the morphodynamics of distributary channel network growth on river deltas. The interface between deep channels and the shallow, unchannelized delta front deposits is modeled as a moving boundary. Steady flow over the unchannelized delta front is friction dominated and modeled by Laplace's equation. Shear stress along the network boundary produces nonlinear erosion rates at the interface, causing the boundary to move and network elements (channels and branches) to form. The model was run for boundary conditions resembling the Wax Lake Delta in coastal Louisiana, 20 parameterizations of sediment transport, and 3 …


Structural Control Of Mesic Vegetation Communities Within The Owl And Bear Creek Watersheds, Fort Hood Military Installation, Texas, Melinda S. Faulkner, Matthew Mcbroom, Kenneth W. Farrish, Kevin Stafford Jun 2019

Structural Control Of Mesic Vegetation Communities Within The Owl And Bear Creek Watersheds, Fort Hood Military Installation, Texas, Melinda S. Faulkner, Matthew Mcbroom, Kenneth W. Farrish, Kevin Stafford

Faculty Publications

The Fort Hood Military Installation is a karst landscape, dominated by Lower Cretaceous carbonates of the Trinity and Fredericksburg groups. The study area is the northeastern peninsula known as the Owl Mountain Province, utilized by the U.S. Army for troop maneuvers and training. The geomorphic evolution of the province has been controlled by the structural development of incised canyons in the Owl and Bear creek watersheds, following the deformational trend of the Balcones/Ouachita fault system and the transverse Belton High-Central Texas Reef Trend. These trends control cave development in the subsurface, karst manifestations at the surface, joints in outcrop, stream …


Grain Size And Vegetation As Controlling Variables Of Stream Channel Morphology, Grant Colip May 2019

Grain Size And Vegetation As Controlling Variables Of Stream Channel Morphology, Grant Colip

Senior Honors Projects, 2010-2019

Streams are one of the major driving forces that shape the landscapes in the Shenandoah Valley of Virginia and the eastern United States as a whole, and they serve an important role in transporting both water and sediment to the Atlantic Ocean. However, streams are often modified for human use, thus altering their natural equilibrium. These alterations have frequently led to the degradation of channel stability as well as damage to property and infrastructure. A better understanding of how both grain size (D50) and vegetation impact stream sinuosity (S) is needed to analyze the prevalence of channel degradation …


Legacy Sediment Controls On Post-Glacial Beaches Of Massachusetts, Alycia Ditroia Mar 2019

Legacy Sediment Controls On Post-Glacial Beaches Of Massachusetts, Alycia Ditroia

Masters Theses

Here we examine seasonal grain-size trends on 18 beaches in the Northeastern US and dispersed along the post-glacial coast of Massachusetts (USA) in order to explore the mechanisms influencing median grain size and slope. Over 800 grain size samples were collected along 200 summer and winter cross-shore beach elevation surveys. Obtained grain size and beach slope data are compared to coastal morphology, sediment source, wave height, and tidal magnitude in order to ascertain controls on beach characteristics. In general, median grain size increases with intertidal beach slope in the study region. However, grain sizes along post-glaciated beaches in the study …


Short Communication: Challenges And Applications Of Structure-From-Motion Photogrammetry In A Physical Model Of A Braided River, Peter Ashmore, Pauline Leduc, Sarah Peirce Jan 2019

Short Communication: Challenges And Applications Of Structure-From-Motion Photogrammetry In A Physical Model Of A Braided River, Peter Ashmore, Pauline Leduc, Sarah Peirce

Geography & Environment Publications

For extending the applications of structure-from-motion (SfM) photogrammetry in river flumes, we present the main challenges and methods used to collect a large dataset ( > 1000 digital elevation models, DEMs) of high-quality topographic data using close-range SfM photogrammetry. Automatic target detection, batch processing, and considerations for image quality were fundamental to the successful implementation of the SfM technique on such a large dataset, which was used primarily for capturing details of gravel-bed braided river morphodynamics and sedimentology. While the applications of close-range SfM photogrammetry are numerous, we include sample results from DEM differencing, which was used to quantify morphology change …


Determining Rates Of Landscape Response To Tectonic Forcing Across A Range Of Temporal Scales And Erosional Mechanisms: Teton Range, Wy, Meredith Swallom Jan 2019

Determining Rates Of Landscape Response To Tectonic Forcing Across A Range Of Temporal Scales And Erosional Mechanisms: Teton Range, Wy, Meredith Swallom

Theses and Dissertations--Earth and Environmental Sciences

Understanding how mountain landscapes respond to variations in tectonic forcing over a range of temporal scales in active mountain belts remains as a prominent challenge in tectonic and geomorphological studies. Although a number of empirical and numerical studies have examined this problem, many of them were complicated by issues of scale and climatic variability. More specifically, the relative efficiencies of fluvial and glacial erosion, which are presumably controlled by climate, are difficult to unravel. The Teton Range in Wyoming, which results from motion on the crustal-scale Teton fault, is an ideal natural laboratory for addressing this challenge as the tectonic …


Mass Wasting Investigation And Assessment In The Midwest: Case Study Of The Minnesota River Valley, New Ulm To St. Peter, Minnesota, Usa, Melissa Kohout Jan 2019

Mass Wasting Investigation And Assessment In The Midwest: Case Study Of The Minnesota River Valley, New Ulm To St. Peter, Minnesota, Usa, Melissa Kohout

All Graduate Theses, Dissertations, and Other Capstone Projects

Many mass- wasting studies have been conducted worldwide, however, investigations have focused in mountainous or coastal regions. This has proven problematic in areas lacking those features yet are experiencing mass wasting. Several anthropogenic risks, economic loss, and environmental issues are associated with mass wasting such as destruction of property, loss of life, and sediment pollution. The midwestern USA, is generally considered a low relief region, therefore limited data exist for mass wasting occurrence. Within the last decade, however, several events have occurred across Minnesota with little understanding of the ongoing hillslope processes leading to failure. The Minnesota River valley is …


Three-Dimensional Bedrock Channel Evolution With Smoothed Particle Hydrodynamics, Nick Richmond Dec 2018

Three-Dimensional Bedrock Channel Evolution With Smoothed Particle Hydrodynamics, Nick Richmond

Electronic Theses and Dissertations

Bedrock channels are responsible for balancing and communicating tectonic and climatic signals across landscapes, but it is difficult and dangerous to observe and measure the flows responsible for removing weakly-attached blocks of bedrock from the channel boundary. Consequently, quantitative descriptions of the dynamics of bedrock removal are scarce. Detailed numerical simulation of violent flows in three dimensions has been historically challenging due to technological limitations, but advances in computational fluid dynamics aided by high-performance computing have made it practical to generate approximate solutions to the governing equations of fluid dynamics. From these numerical solutions we gain detailed knowledge of the …


Late Quaternary Evolution And Stratigraphic Framework Influence On Coastal Systems Along The North-Central Gulf Of Mexico, Usa, Robert Hollis Dec 2018

Late Quaternary Evolution And Stratigraphic Framework Influence On Coastal Systems Along The North-Central Gulf Of Mexico, Usa, Robert Hollis

Master's Theses

Coastal systems in the Gulf of Mexico are threatened to reduced sediment supply, storm impacts and relative sea level rise (RSLR). The geologic record can provide insights of geomorphic threshold crossings (formation, progradation, transgression, destruction) to these forcing mechanisms to predict future barrier evolution to climate change. The stratigraphic framework and antecedent topography directly influence coastal evolution over geologic timescales. This study synthesizes ~2100km of geophysical data, 700+ sediment cores, and 63 radiocarbon dates to regionally map two sequence boundaries, multiple ravinement surfaces and fourteen depositional facies. One marine isotope stage (MIS) 6 valley’s fill provided up to 300 x10 …


Keeping Pace With Relative Sea Level Rise: Marsh Platform Monitoring Shows Minimal Sediment Deficit Along The Louisiana Coast, Kelly Marie Sanks Dec 2018

Keeping Pace With Relative Sea Level Rise: Marsh Platform Monitoring Shows Minimal Sediment Deficit Along The Louisiana Coast, Kelly Marie Sanks

Graduate Theses and Dissertations

Recent reports estimate that the marshes of the Mississippi Delta receive just 30% of the sediment necessary to sustain current land area1. An extensive monitoring campaign by the USGS and LCPRA provides direct measurements of sediment accumulation, subsidence rates, and deposit characteristics along the coast over the past 10 years2, allowing us to directly evaluate this sediment balance. By interpolating bulk density, organic fraction, and vertical accretion rates from 273 sites, a direct measurement of organic and inorganic sediment accumulation can be made. Results show that a total of 82 MT/year of sediment is delivered to the coast. Using a …


Remains Of The 19th Century: Deep Storage Of Contaminated Hydraulic Mining Sediment Along The Lower Yuba River, California, Tyler Nakamura, Michael Bliss Singer, Emmanuel Gabet Nov 2018

Remains Of The 19th Century: Deep Storage Of Contaminated Hydraulic Mining Sediment Along The Lower Yuba River, California, Tyler Nakamura, Michael Bliss Singer, Emmanuel Gabet

Faculty Publications

Since the onset of hydraulic gold mining in California’s Sierra Nevada foothills in 1852, the environmental damage caused by displacement and storage of hydraulic mining sediment (HMS) has been a significant ecological problem downstream. Large volumes of mercury-laden HMS from the Yuba River watershed were deposited within the river corridor, creating the anthropogenic Yuba Fan. However, there are outstanding uncertainties about how much HMS is still contained within this fan. To quantify the deep storage of HMS in the Yuba Fan, we analyzed mercury concentrations of sediment samples collected from borings and outcrops at multiple depths. The mercury concentrations served …


Rates Of Planimetric Change In A Proglacial Gravel-Bed Braided River: Field Measurement And Physical Modeling, Lara Middleton, Peter Ashmore, Pauline Leduc, Darren Sjogren Oct 2018

Rates Of Planimetric Change In A Proglacial Gravel-Bed Braided River: Field Measurement And Physical Modeling, Lara Middleton, Peter Ashmore, Pauline Leduc, Darren Sjogren

Geography & Environment Publications

Planimetric change was measured on daily hydrographs over two meltwater seasons using time-lapse images of the proglacial, gravel, braided, Sunwapta River, Canada. Significant planimetric change occurred on 10-15 days per year. Area of planimetric change correlated with peak and total daily meltwater hydrograph discharge. A clear threshold discharge can be identified below which no planform activity occurs, an intermediate range over which change occurs conditionally, and a peak flow range at which significant change always occurs. Field conditions were reproduced in a physical model in a laboratory flume. Photogrammetric DEMs of bed morphology and measurements of bedload output were made …


Controls On Speleogenesis In The Upper-Mississippian Pennington Formation On The Western Cumberland Plateau Escarpment, Hali Steinmann Oct 2018

Controls On Speleogenesis In The Upper-Mississippian Pennington Formation On The Western Cumberland Plateau Escarpment, Hali Steinmann

Masters Theses & Specialist Projects

Much of the pioneering work on caves of the Cumberland Plateau (province spanning Tennessee, Kentucky, Alabama, and Georgia) has been stratigraphically located within the Mississippian Bangor and Monteagle Limestones, wherein some of the region’s largest and most spectacular caves occur. Of interest to the understanding of this karst landscape, but severely underrepresented in the literature thereof, are caves and karst features in a heterogeneous sequence of clastics and carbonates known collectively as the Pennington Formation (Upper Mississippian). This work consisted of a regional study of Pennington caves on the western Cumberland Plateau escarpment (Alabama and Tennessee), and a case study …


Evidence For Subsurface Origin Of Boulder Caves, Roofed Slots And Boulder-Filled Canyons (Broumov Highland, Czechia), Filip Duszyński, Kacper Jancewicz, Piotr Migoń Sep 2018

Evidence For Subsurface Origin Of Boulder Caves, Roofed Slots And Boulder-Filled Canyons (Broumov Highland, Czechia), Filip Duszyński, Kacper Jancewicz, Piotr Migoń

International Journal of Speleology

The backslope of a sandstone cuesta in the Broumov Highland (Czechia) is cut by a complex network of canyons. Long sections of canyons have thick boulder fills which are difficult to reconcile with simple rock fall and talus development scenario. Boulder caves occur within these fills and their lowermost parts are drained by streams that evacuate fine loose sandy material produced by weathering and mechanical erosion. These boulder fills are explained as largely in situ, residual features, left after subsurface selective disintegration of rock mass, mainly joint-guided, and removal of grains by underground water. Evacuation of fines leaves voids …


The Periglacial Landscape Of Mars: Insight Into The 'Decameter-Scale Rimmed Depressions' In Utopia Planitia, Arya Bina Aug 2018

The Periglacial Landscape Of Mars: Insight Into The 'Decameter-Scale Rimmed Depressions' In Utopia Planitia, Arya Bina

Electronic Thesis and Dissertation Repository

Currently, Mars appears to be in a ‘frozen’ and ‘dry’ state, with the clear majority of the planet’s surface maintaining year-round sub-zero temperatures. However, the discovery of features consistent with landforms found in periglacial environments on Earth, suggests a climate history for Mars that may have involved freeze and thaw cycles. Such landforms include hummocky, polygonised, scalloped, and pitted terrains, as well as ice-rich deposits and gullies, along the mid- to high-latitude bands, typically with no lower than 20o N/S. The detection of near-surface and surface ice via the Phoenix lander, excavation of ice via recent impact cratering activity as …


Impact Craters On Titan: Finalizing Titan's Crater Population, Joshua E. Hedgepeth Aug 2018

Impact Craters On Titan: Finalizing Titan's Crater Population, Joshua E. Hedgepeth

Electronic Thesis and Dissertation Repository

Titan is one of the most dynamic moons in the solar system. It is smaller than Earth and much colder, yet Titan is eerily similar to Earth, with rivers, rain, and seas, as well as sand seas that wrap around the equator. However, the rivers are made of hydrocarbons rather than water and the sand made of organics rather rock. We can use Titan’s impact craters to study how these processes modify the surface by comparing the craters depths, diameters and rim heights of Titan’s craters with fresh craters. Therefore, we have used the complete data set from NASA’s Cassini …


Analysis Of The Parkway Drive Landslide, North Salt Lake, Ut, Brianna V. Hill Aug 2018

Analysis Of The Parkway Drive Landslide, North Salt Lake, Ut, Brianna V. Hill

All Graduate Plan B and other Reports, Spring 1920 to Spring 2023

On August 5th, 2014, a hillside failed behind a North Salt Lake City, UT neighborhood threatening several homes. Aerial Photography, Digital Elevation Models (DEM), geochemistry, rain gage and seismic data were used to test the influence of contributing factors in this landslide failure. Aerial photographs available from 1993 to present were examined for signs of tension cracks suggesting impending ground motion, as well as documentation of human modification along the hillslope. Repeat DEM analysis of elevation and slope of the hillside before and after the slide were examined to characterize the pre-failure hillslope and subsequent landslide. Geochemical analyses …


Effects Of Natural And Anthropogenic Forcing On Marsh Channel Evolution, Jeremiah Robinson Jul 2018

Effects Of Natural And Anthropogenic Forcing On Marsh Channel Evolution, Jeremiah Robinson

LSU Master's Theses

Wetlands have many ecological and physical properties that are essential for coastal communities. These ecosystems sustain local economies, provide essential habitats, are a source of numerous ecological and biological services, and protect coastal populations from storms. Of the many wetland types, salt marshes are among the most vulnerable to environmental changes. Salt marshes quickly respond to natural and human-driven perturbations and their high rate of loss in the last century is cause for concern.

In this project the rate of marsh loss driven by channel widening was measured through a comparative analysis of modern high resolution images and historic aerial …


Tectonic Controls On Alluvial Fan Dissection In The El Paso Mountains, Michael Thomas Gaffney Jun 2018

Tectonic Controls On Alluvial Fan Dissection In The El Paso Mountains, Michael Thomas Gaffney

Natural Resources Management and Environmental Sciences

The localized dissection of alluvial fans along the western El Paso Mountains is under question. A relatively minor, south dipping normal fault, previously unmentioned in scientific literature, cuts across Quaternary terraces and alluvial fans in the piedmont of the El Paso Mountains. The linear trend of footwall uplift and the pattern of stream incision into the footwall adjacent to the linear trend of footwall uplift reveal that fan dissection is a result of base level fall caused by ongoing tectonism along the El Paso fault system. The regional importance is discussed as the timing of faulting reveals relatively recent uplift …


Optimizing Uav Surveys For Coastal Morphodynamics: Estimation Of Spatial Uncertainty As A Function Of Flight Acquisition And Post-Processing Factors, Mark Lundine May 2018

Optimizing Uav Surveys For Coastal Morphodynamics: Estimation Of Spatial Uncertainty As A Function Of Flight Acquisition And Post-Processing Factors, Mark Lundine

Celebration of Learning

Recent developments in unmanned aerial vehicles (UAVs) and photogrammetry software enable the rapid collection of aerial photography and video over study areas of varying sizes, thereby providing ease of use and accessibility for studies of coastal geomorphology. However, there remains uncertainty over UAV survey techniques, with disagreement on specific flight patterns, flight altitudes, photograph amounts, ground control point (GCP) amounts, GCP spacing schemes, drone models, and which SfM software to use, amongst other study-specific parameters.

A controlled field test (of 1.2 hectares) was performed to determine SfM’s sensitivity to the following flight parameters: altitude (60 m, 80 m, 120 m), …


Spatial And Temporal Analysis Of Island Morphology In Lower Pool 18 Of The Mississippi River, Marissa C. Iverson May 2018

Spatial And Temporal Analysis Of Island Morphology In Lower Pool 18 Of The Mississippi River, Marissa C. Iverson

Celebration of Learning

The Upper Mississippi River System has a significant trend in island loss due to river engineering structures. However, Lower Pool 18 is observed as a counterexample to the island loss pattern with its island development near Lock and Dam 18 during the past 80 years. This research is modeled after a study done in Lower Pool 6 of the Upper Mississippi River where an island development was found to contradict the island loss prevalence. The Lower Pool 18 research’s goal is to map, describe, and explain spatial patterns of islands growth, persistence and loss. Historical maps and aerial photographs of …


Geochemical Dynamics And Nitrous Oxide Release From The Hyporheic Zone Of Streams, Annika Marie Quick May 2018

Geochemical Dynamics And Nitrous Oxide Release From The Hyporheic Zone Of Streams, Annika Marie Quick

Boise State University Theses and Dissertations

The hyporheic zones of streams and rivers, consisting of the sediments beneath and immediately adjacent to the stream channel, are an important site of geochemical processing. Due to the difficulty of measuring these geochemical processes in the hyporheic zone in situ with meaningful spatial and temporal resolution, we conducted multiple column and large-scale flume experiments to model 1D and 2D hyporheic flow paths and observed important geochemical reactions, including the production and consumption of nitrous oxide (N2O). N2O is a significant greenhouse gas, but the controls on its emissions from streams are poorly constrained. We describe …


Glacial History Of The Tsagaan Gol- Potanin Glacier Valley, Altai Mountains, Mongolia, Mariah J. Radue May 2018

Glacial History Of The Tsagaan Gol- Potanin Glacier Valley, Altai Mountains, Mongolia, Mariah J. Radue

Electronic Theses and Dissertations

The last glacial termination (~19-11 ka) marks the end of the last ice age and the transition to modern interglacial conditions. The mechanisms that triggered deglaciation are unresolved. Various hypotheses for deglacial warming involve changes in Earth’s orbit, an 80-ppm increase in atmospheric CO­2, a ‘bipolar seesaw’ in oceanic-heat redistribution, and shifting wind belts. Here, I present a 10Be surface-exposure chronology for a system of glacial landforms in the Tsagaan Gol-Potanin Glacier valley in the Mongolian Altai (49°N, 88°E) to determine the nature of the termination in interior Asia. Located near the center of Earth’s largest continent, …


Expanding The "Active Layer", Peter Ashmore, Sarah Peirce, Pauline Leduc Feb 2018

Expanding The "Active Layer", Peter Ashmore, Sarah Peirce, Pauline Leduc

Geography & Environment Publications

Church and Haschenburger (2017) make helpful distinctions around the issue of defining the active layer, with which we agree. We propose expanding discussion and definition of the ”active layer” in fluvial bedload transport to include the concept of the “morphological active layer”. This is particularly applicable to laterally unstable rivers (such as braided rivers) in which progressive morphological change over short time periods is the process by which much of the bedload transport occurs. The morphological active layer is also distinguished by variable lateral and longitudinal extent continuity over a range of flows and transport intensity. We suggest that the …