T.D. Lorenson

Seasonal Electrical Resistivity Surveys of a Coastal Bluff, Barter Island, North Slope Alaska

Select coastal regions of the North Slope of Alaska are experiencing high erosion rates that can be attributed in part to recent warming trends and associated increased storm intensity and frequency. The upper sediment column of the coastal North Slope of Alaska can be described as continuous permafrost underlying a thin (typically less than 1–2 m) active layer that responds variably to seasonal thaw cycles. Assessing the temporal and spatial variability of the active layer and underlying permafrost is essential to better constrain how heightened erosion may impact material fluxes to the atmosphere and the coastal ocean, and how enhanced thaw cycles may impact the stability of the coastal bluffs. In this study, multi-channel electrical resistivity tomography (ERT) was used to image shallow subsurface features of a coastal bluff west of Kaktovik, on Barter Island, northeast Alaska. A comparison of a suite of paired resistivity surveys conducted in early and late summer 2014 provided detailed information on nhow the active layer and permafrost are impacted during the short Arctic summer. Such results are useful in the development of coastal resilience models that tie together fluvial, terrestrial, climatic, geologic, and oceanographic forcings on shoreline stability.

Eel Canyon Slump Scar and Associated Fluid Venting

Autonomous underwater vehicles have been used to characterize Eel Slump, a slide scar located south of Eel Canyon, California. The presence of a well developed dendritic network on the headwall with gullies tens of meters deep, thick sediment drape cover on the slide scar sole, and the absence of fresh surfaces on the scarp suggest that the mass failure(s) that produced this feature did not take place in the recent past. Thermogenic oil and gas emanating from a large mound in the sole of the slide scar were sampled with a remotely operated vehicle. Other distinctive morphologies observed from the seafloor of the slide scar indicate fluid seep has occurred at multiple sites within the slide scar sole.