THREE-DIMENSIONAL OPTICAL SCANNING TO ASSESS EROSION OF ARCHAEOLOGICAL SITES, YELLOWSTONE NATIONAL PARK, U.S.A.

2004

THREE-DIMENSIONAL OPTICAL SCANNING TO ASSESS EROSION OF ARCHAEOLOGICAL SITES, YELLOWSTONE NATIONAL PARK, U.S.A.

Stephen K. Boss, Dept. of Geosciences, 113 Ozark Hall, University of Arkansas, Fayetteville, AR 72701, Barbara E. Pickup Environmental Dynamics Program, Mo Salem, Environmental Dynamics Program

High resolution (1-cm), three-dimensional images of archaeological sites exposed on the shore of Yellowstone Lake (Yellowstone National Park, USA) were acquired utilizing the High Accuracy/Resolution Landscape and Surface Characterization System (HARLS-CS) from the Center for Advanced Spatial Technologies at the University of Arkansas. The HARLS-CS deployed during August 2004 in Yellowstone National Park was composed of an Optech ILRIS 3D laser profiler, Trimble 5700/5800 total station with GPS, and supporting software (e.g. Innovmetric PolyWorks and EOS PhotoModeler). Preliminary scans of archaeological sites at Osprey Beach and nearshore bluffs adjacent to 48YE449 and 48YE395 provided extraordinarily detailed 3-D imagery that will serve as reference images to quantify erosion of these sites resulting from rain, wind, wave, and ice activity along the lakeshore during the next year. This demonstration project will provide resource managers unparalleled ability to accurately document degradation of important archaeological sites resulting from natural processes and will provide insight into the magnitude of lakeshore erosion/deposition with the aim of developing strategies for long-term management of critical cultural resources in the nation’s oldest national park.

2004

A 50-YEAR RECORD OF SHORELINE CHANGE AT YELLOWSTONE LAKE, YELLOWSTONE NATIONAL PARK, USA

Pickup, Barbara E., Environmental Dynamics Program, University of Arkansas, Fayetteville, AR 72701, and Boss, Stephen K., Department of Geosciences, University of Arkansas

Analysis of repeat aerial photographs from 1954-2002 of the northern shoreline of the West Thumb arm of Yellowstone Lake indicated geomorphic changes of this single area were very complex. Some segments of the shoreline were receding while other segments were simultaneously advancing, yet the caldera was alternating between inflation and deflation cycles throughout this period. Portions of the well-developed baymouth bar that separates Yellowstone Lake from the lagoon at the outflow of Arnica Creek also exhibited up to 80 m of eastward longshore transport. These results suggest that the interaction between caldera inflation/deflation, sediment supply, lake level, and shoreline change is complex.

2003

BAY MOUTH BARS, LOOP BARS, AND RECURVED SPITS IN YELLOWSTONE LAKE: NORTH AMERICA’S HIGHEST ELEVATION “COASTAL” LANDFORMS

Boss, Stephen K., Department of Geosciences, 113 Ozark Hall, University of Arkansas, Fayetteville, AR 72701

Yellowstone Lake (Yellowstone National Park, USA) is among the world’s largest high-altitude lakes (elevation 2,357 m above MSL). A reconnaissance survey of the lake’s perimeter identified a number of landforms more commonly associated with coastal environments (bay mouth bars, loop bars, recurved spits). Though similar features may commonly be observed along the shorelines of large lakes, they are generally unknown from alpine lakes. As such, the “coastal” landforms of Yellowstone Lake represent a unique yet unstudied aspect of Yellowstone geomorphology and are the highest elevation “coastal” landforms in North America. Many of the best developed accretionary bay mouth bars, loop bars, and spits appear to correspond to the axis of maximum uplift within Yellowstone caldera. This suggests that resurgent uplift of the caldera associated with Yellowstone hot spot dynamics provides a littoral shelf where sediment derived from erosion of unconsolidated volcanic agglomerates along the lake shore may be transported by longshore drift forming large sedimentary bodies. A transect across the best developed bay mouth bar in the West Thumb arm of Yellowstone Lake indicates that it displays several subtle progradational ridges as well as evidence of sediment transport resulting from overwash. Future detailed studies of “coastal” landforms of Yellowstone Lake could provide insights into the geologic history of lake level variations related to episodic inflation-deflation of the central caldera.

2004

GEOMORPHIC SIGNIFICANCE OF LAKESHORE LANDFORMS OF YELLOWSTONE LAKE, YELLOWSTONE NATIONAL PARK, USA

Boss, Stephen K., Department of Geosciences, 113 Ozark Hall, University of Arkansas, Fayetteville, AR 72701; Pickup, Barbara E., Environmental Dynamics Program, University of Arkansas, 113 Ozark Hall, University of Arkansas, Fayetteville, AR 72701

Yellowstone Lake (Yellowstone National Park, USA) is among the world’s largest high-altitude lakes (elevation 2,357 m above MSL). Well-developed lakeshore landforms include bay mouth/bay head bars and recurved spits. Development and evolution of sedimentary landforms is unusual in caldera lakes because lake margins are often very steep and descend to relatively great depths. At Yellowstone Lake, the best-developed lakeshore landforms are associated with the axis of maximum uplift of Yellowstone caldera, suggesting that tectonic processes are a first-order influence on geomorphic evolution of shoreline features. Along the northern lakeshore, relatively rapid uplift associated with caldera dynamics created a shallow (<10 m deep) platform on which nearshore landforms have developed. Areal dimensions of lakeshore landforms correlate with areal dimensions of the uplifted shallow terrace and the observed long-term uplift history of the caldera. Secondary influences on geomorphic evolution of lakeshore bars and spits are lake level oscillations (driven by seasonal and interannual climatic variability). Sediment supply to lakeshore settings is a tertiary influence on geomorphic evolution of lakeshore landforms, responding to uplift/subsidence and climatic variability. Investigating and understanding decadal records of lakeshore change will provide insights into the geomorphic significance of lakeshore landforms with respect to caldera dynamics, tectonically- and climatically-driven lake level oscillations, and variations in sediment supply/transport processes. These data may ultimately provide greater insight into the geologic history of the Yellowstone Lake system.