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

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). Many of the best developed landforms 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 explosion breccia along the lake shore may be transported by longshore drift forming large sedimentary bodies. 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.