Search

Search Results

• 1. [Article] Debris flows in glaciated catchments : a case study on Mount Rainier, Washington

  Debris flows, which occur in mountain settings worldwide, have been particularly damaging in the glaciated basins flanking the stratovolcanoes in the Cascade Range of the northwestern United States. This ...

  Citation × Citation Citation Abstract Copy Title: Debris flows in glaciated catchments : a case study on Mount Rainier, Washington Author: Legg, Nicholas T. Debris flows, which occur in mountain settings worldwide, have been particularly damaging in the glaciated basins flanking the stratovolcanoes in the Cascade Range of the northwestern United States. This thesis contains two manuscripts that respectively investigate the (1) initiation processes of debris flows in these glaciated catchments, and (2) debris flow occurrence and its effect on valley bottoms over the last thousand years. In a 2006 storm, seven debris flows initiated from proglacial gullies of separate basins on the flanks of Mount Rainier. Gully heads at glacier termini and distributed collapse of gully walls imply that clear water was transformed to debris flow through progressive addition of sediment along gully lengths. In the first study, we analyze gully changes, reconstruct runoff conditions, and assess spatial distributions of debris flows to infer the processes and conditions necessary for debris flow initiation in glaciated catchments. Gully measurements suggest that sediment bulking requires steep gradients, abundant unstable material, and sufficient gully length. Reconstruction of runoff generated during the storm suggests that glaciers are important for generating the runoff necessary for debris flow initiation, particularly because infiltration capacities on glacial till covered surfaces well exceed measured rainfall rates. Runoff generation from glaciers and abundant loose debris at their termini explain why all debris flows in the storm initiated from proglacial areas. Proglacial areas that produced debris flows have steeper drainage networks with significantly higher elevations and lower drainage areas, suggesting that debris flows are associated with high elevation glaciers with relatively steep proglacial areas. This correlation reflects positive slope-elevation trends for the Mount Rainier volcano. An indirect effect of glacier change is thus the change in the distribution of ice-free slopes, which influence a basin’s debris flow potential. These findings have implications for projections of debris flow activity in basins experiencing glacier change. The second study uses a variety of dating techniques to reconstruct a chronology of debris flows in the Kautz Creek valley on the southwest flank of Mount Rainier (Washington). Dendrochronologic dating of growth disturbances combined with lichenometric techniques constrained five debris flow ages from 1712 to 1915 AD. We also estimated ages of three debris flows ranging in age from ca. 970 to 1661. Run-out distances served as a proxy for debris flow magnitude, and indicate that at least 11, 2, and 1 debris flow(s) have traveled at least 1, 3, and 5 km from the valley head, respectively since ca. 1650. Valley form reflects the frequency-magnitude relationship indicated by the chronology. In the upper, relatively steep valley, discrete debris flow snouts and secondary channels are abundant, suggesting a process of debris flow conveyance, channel plugging, and channel avulsion. The lower valley is characterized by relatively smooth surfaces, an absence of bouldery debris flow snouts, few secondary channels, and relatively old surface ages inferred from the presence of tephra layers. We infer that the lower valley is deposited on by relatively infrequent, large magnitude, low-yield strength debris flows like an event in 1947, which deposited wide, tabular lobes of debris outside of the main channel. Debris flows during the Little Ice Age (LIA) predominantly traveled no further than the upper valley. Stratigraphic evidence suggests that the main Kautz Creek channel was filled during the LIA, enhancing debris flow deposition on the valley surface and perhaps reducing run-out lengths. Diminished areas and gradients in front of glaciers during the LIA also likely contributed to decreased run-out lengths. These findings suggest that changes in debris flow source and depositional zones resulting from temperature and glacier cycles influence the magnitude and run-out distances of debris flows, and the dynamics of deposition in valley bottoms. Title: Debris flows in glaciated catchments : a case study on Mount Rainier, Washington Author: Legg, Nicholas T. Debris flows, which occur in mountain settings worldwide, have been particularly damaging in the glaciated basins flanking the stratovolcanoes in the Cascade Range of the northwestern United States. This thesis contains two manuscripts that respectively investigate the (1) initiation processes of debris flows in these glaciated catchments, and (2) debris flow occurrence and its effect on valley bottoms over the last thousand years. In a 2006 storm, seven debris flows initiated from proglacial gullies of separate basins on the flanks of Mount Rainier. Gully heads at glacier termini and distributed collapse of gully walls imply that clear water was transformed to debris flow through progressive addition of sediment along gully lengths. In the first study, we analyze gully changes, reconstruct runoff conditions, and assess spatial distributions of debris flows to infer the processes and conditions necessary for debris flow initiation in glaciated catchments. Gully measurements suggest that sediment bulking requires steep gradients, abundant unstable material, and sufficient gully length. Reconstruction of runoff generated during the storm suggests that glaciers are important for generating the runoff necessary for debris flow initiation, particularly because infiltration capacities on glacial till covered surfaces well exceed measured rainfall rates. Runoff generation from glaciers and abundant loose debris at their termini explain why all debris flows in the storm initiated from proglacial areas. Proglacial areas that produced debris flows have steeper drainage networks with significantly higher elevations and lower drainage areas, suggesting that debris flows are associated with high elevation glaciers with relatively steep proglacial areas. This correlation reflects positive slope-elevation trends for the Mount Rainier volcano. An indirect effect of glacier change is thus the change in the distribution of ice-free slopes, which influence a basin’s debris flow potential. These findings have implications for projections of debris flow activity in basins experiencing glacier change. The second study uses a variety of dating techniques to reconstruct a chronology of debris flows in the Kautz Creek valley on the southwest flank of Mount Rainier (Washington). Dendrochronologic dating of growth disturbances combined with lichenometric techniques constrained five debris flow ages from 1712 to 1915 AD. We also estimated ages of three debris flows ranging in age from ca. 970 to 1661. Run-out distances served as a proxy for debris flow magnitude, and indicate that at least 11, 2, and 1 debris flow(s) have traveled at least 1, 3, and 5 km from the valley head, respectively since ca. 1650. Valley form reflects the frequency-magnitude relationship indicated by the chronology. In the upper, relatively steep valley, discrete debris flow snouts and secondary channels are abundant, suggesting a process of debris flow conveyance, channel plugging, and channel avulsion. The lower valley is characterized by relatively smooth surfaces, an absence of bouldery debris flow snouts, few secondary channels, and relatively old surface ages inferred from the presence of tephra layers. We infer that the lower valley is deposited on by relatively infrequent, large magnitude, low-yield strength debris flows like an event in 1947, which deposited wide, tabular lobes of debris outside of the main channel. Debris flows during the Little Ice Age (LIA) predominantly traveled no further than the upper valley. Stratigraphic evidence suggests that the main Kautz Creek channel was filled during the LIA, enhancing debris flow deposition on the valley surface and perhaps reducing run-out lengths. Diminished areas and gradients in front of glaciers during the LIA also likely contributed to decreased run-out lengths. These findings suggest that changes in debris flow source and depositional zones resulting from temperature and glacier cycles influence the magnitude and run-out distances of debris flows, and the dynamics of deposition in valley bottoms. Close

• 2. [Article] Changing landscape, climate, and life during the age of mammals: interpreting paleontology, evolving ecosystems, and climate change in the Cenozoic fossil parks

  This thesis develops a manual for interpreters at six National Park Service areas established to preserve and interpret fossils of the Cenozoic Era: Fossil Butte National Monument (Wyoming), John Day Fossil ...

  Citation × Citation Citation Abstract Copy Title: Changing landscape, climate, and life during the age of mammals: interpreting paleontology, evolving ecosystems, and climate change in the Cenozoic fossil parks Author: Kenworthy, Jason P. This thesis develops a manual for interpreters at six National Park Service areas established to preserve and interpret fossils of the Cenozoic Era: Fossil Butte National Monument (Wyoming), John Day Fossil Beds National Monument (Oregon), Badlands National Park (South Dakota), Florissant Fossil Beds National Monument (Colorado), Agate Fossil Beds National Monument (Nebraska), and Hagerman Fossil Beds National Monument (Idaho). The manual will help interpreters place their park’s story into the context of three components of paleoecosystems preserved in each park: changes in geologic landscapes, global climate, and the evolution of mammals. It also provides context for interpreting modern climate change. The colorful landscapes of the Cenozoic fossil parks preserve evidence of changing landscapes, climates, and life as well as clues about change affecting our future. Because the six parks are nationally and globally significant paleontological sites, they also offer interpretive opportunities to connect visitors to the science of paleontology. The manual is written for interpreters with a variety of geology, other science and humanities backgrounds. The first three chapters provide a basic foundation of paleontological knowledge and interpretive resources applicable to all of the parks. Chapter 1 is an introduction to the scope and significance of the fossils and paleoecosystems preserved in each of the Cenozoic fossil parks. Chapter 2 outlines NPS interpretive theory and offers practical information for developing paleontology interpretation and interpreting longterm paleoecosystem evolution. Chapter 3 provides geologic content and interpretive methods for answering three common questions visitors ask: How old are these fossils? What is a fossil? and Were all these fossils found here? Interpretive responses to these questions allow visitors to connect with the Cenozoic Era, fossilization processes, and the profound sense of place afforded by the fossil parks. Chapters 4, 5, and 6 summarize how the major components of ecosystems changed between the extinction of dinosaurs 65 million years ago and the beginning of the Pleistocene “ice ages” 2.6 million years ago. Chapter 4 details the active geologic processes—mountain building and volcanic activity—of the American West during this time period and how these processes helped form and preserve the paleoecosystems of the parks. Chapter 5 places the parks’ paleoecosystems in chronological order and relates them to the global climate transition from the “greenhouse” world (nearly-tropical forests and lakes at Fossil Butte NM, John Day Fossil Beds NM, Badlands NP, and Florissant Fossil Beds NM) of 65 to 34 million years ago, to the “icehouse” world (cooler and drier woodlands, savannahs, and grasslands at John Day Fossil Beds NM, Badlands NP, Agate Fossil Beds NM, and Hagerman Fossil Beds NM) beginning 34 million years ago and continuing today. Chapter 6 traces the evolution of the horse during this time of global change from a four-toed, dog-sized browser to a hoofed, zebra-sized grazer on the grasslands of the American West. Chapter 7 describes the “ice ages” that followed the stories of the Cenozoic fossil parks. It also places the global climatic and ecosystem changes told by the Cenozoic fossil parks in the context of modern, rapid, anthropogenic climate changes. Each chapter includes “Digging Deeper” boxes that provide more detailed geologic content, or interpretive suggestions. Title: Changing landscape, climate, and life during the age of mammals: interpreting paleontology, evolving ecosystems, and climate change in the Cenozoic fossil parks Author: Kenworthy, Jason P. This thesis develops a manual for interpreters at six National Park Service areas established to preserve and interpret fossils of the Cenozoic Era: Fossil Butte National Monument (Wyoming), John Day Fossil Beds National Monument (Oregon), Badlands National Park (South Dakota), Florissant Fossil Beds National Monument (Colorado), Agate Fossil Beds National Monument (Nebraska), and Hagerman Fossil Beds National Monument (Idaho). The manual will help interpreters place their park’s story into the context of three components of paleoecosystems preserved in each park: changes in geologic landscapes, global climate, and the evolution of mammals. It also provides context for interpreting modern climate change. The colorful landscapes of the Cenozoic fossil parks preserve evidence of changing landscapes, climates, and life as well as clues about change affecting our future. Because the six parks are nationally and globally significant paleontological sites, they also offer interpretive opportunities to connect visitors to the science of paleontology. The manual is written for interpreters with a variety of geology, other science and humanities backgrounds. The first three chapters provide a basic foundation of paleontological knowledge and interpretive resources applicable to all of the parks. Chapter 1 is an introduction to the scope and significance of the fossils and paleoecosystems preserved in each of the Cenozoic fossil parks. Chapter 2 outlines NPS interpretive theory and offers practical information for developing paleontology interpretation and interpreting longterm paleoecosystem evolution. Chapter 3 provides geologic content and interpretive methods for answering three common questions visitors ask: How old are these fossils? What is a fossil? and Were all these fossils found here? Interpretive responses to these questions allow visitors to connect with the Cenozoic Era, fossilization processes, and the profound sense of place afforded by the fossil parks. Chapters 4, 5, and 6 summarize how the major components of ecosystems changed between the extinction of dinosaurs 65 million years ago and the beginning of the Pleistocene “ice ages” 2.6 million years ago. Chapter 4 details the active geologic processes—mountain building and volcanic activity—of the American West during this time period and how these processes helped form and preserve the paleoecosystems of the parks. Chapter 5 places the parks’ paleoecosystems in chronological order and relates them to the global climate transition from the “greenhouse” world (nearly-tropical forests and lakes at Fossil Butte NM, John Day Fossil Beds NM, Badlands NP, and Florissant Fossil Beds NM) of 65 to 34 million years ago, to the “icehouse” world (cooler and drier woodlands, savannahs, and grasslands at John Day Fossil Beds NM, Badlands NP, Agate Fossil Beds NM, and Hagerman Fossil Beds NM) beginning 34 million years ago and continuing today. Chapter 6 traces the evolution of the horse during this time of global change from a four-toed, dog-sized browser to a hoofed, zebra-sized grazer on the grasslands of the American West. Chapter 7 describes the “ice ages” that followed the stories of the Cenozoic fossil parks. It also places the global climatic and ecosystem changes told by the Cenozoic fossil parks in the context of modern, rapid, anthropogenic climate changes. Each chapter includes “Digging Deeper” boxes that provide more detailed geologic content, or interpretive suggestions. Close

• 3. [Article] Impacts of Swiss needle cast on overstory Douglas-fir forests of the western Oregon Coast Range

  Article appears in Forest Ecology and Management (http://www.elsevier.com/wps/find/journaldescription.cws_home/503310/description#description) and is copyrighted by Elsevier.

  Citation × Citation Citation Abstract Copy Title: Impacts of Swiss needle cast on overstory Douglas-fir forests of the western Oregon Coast Range Author: Stone, Jeffrey K., Black, Bryan A., Shaw, David C. Article appears in Forest Ecology and Management (http://www.elsevier.com/wps/find/journaldescription.cws_home/503310/description#description) and is copyrighted by Elsevier. Title: Impacts of Swiss needle cast on overstory Douglas-fir forests of the western Oregon Coast Range Author: Stone, Jeffrey K., Black, Bryan A., Shaw, David C. Article appears in Forest Ecology and Management (http://www.elsevier.com/wps/find/journaldescription.cws_home/503310/description#description) and is copyrighted by Elsevier. Close