Abstract This trip through SW British Columbia focuses on past and ongoing land movements and flood events, and archaeological sites likely affected by these events. Our route follows a varied terrain of landforms inhabited for millennia by First Nations.

Abstract This volume is intended to provide an up-to-date overview of the approaches, methodologies and techniques devoted to better understanding of the weathering conditions of rock masses on slopes. According to the local conditions, a variety of slope movements may take place and involve weathered rock masses. Shallow and rapid soil slips evolving to debris flows are probably the most common type of slope movement. At the same time, deep-seated, intermittent landslides can also affect large volumes of weathered rocks and soils. Despite the high frequency of landslides in weathered materials, and the damage and casualties they repeatedly cause, little is known about the relationship between weathering and slope movements. This book presents worldwide case studies, where a variety of geological and geomorphological settings are discussed. The content is divided into three sections: the first is devoted to broad aspects of the weathering/landslide processes; the second and third sections include papers dealing with igneous/metamorphic and sedimentary weathered rocks, respectively.

Abstract Slope movements, including types of landslides and extremely slow soil creep ( Varnes, 1978 ), occur throughout the United States and within many national parks. The collection of vital signs of regional landslide information, referred to as monitoring, is not only scientifically useful, but is beneficial for assessment of landslide hazards and risk, which is in turn important for regional operations and planning. Different types of slope movement, such as fall, topple, slide, spread, and flow, can occur in a variety of materials and degrees of slopes. Specific types of landslides ( Fig. 1 ), such as rockfall, earth slump, and debris flow, can occur depending upon the types of geologic materials and movement ( Cruden and Varnes, 1996 ). A landslide can be caused by one or more of several factors, of which geological, morphological, physical, and human factors are the most common. The term landslide trigger refers specifically to an external stimulus, such as intense rainfall, rapid snowmelt, earthquake, volcanic eruption, or stream or coastal erosion. These stimuli initiate an immediate or near-immediate landslide movement by rapidly increasing shear stresses or porewater pressures, by ground acceleration due to seismic activity, by removing lateral support, by reducing the strength of slope materials, or by initiating debris-flow activity. Most landslides with recognized triggers are caused by precipitation: rainfall, snow meltwater, or combinations of both. In rock masses, rain and meltwater penetrate joints and produce hydrostatic pressures. In soils, the increase of pore-water pressures reduces shear resistance ( Schuster and Wieczorek, 2002 ).

ABSTRACT Investigation and design-build construction of the Highway 20 realignment through the Oregon Coast Range provides new insight into paleo-landslides of the Tyee Formation and their slope stability. They are widespread, often extending outside of current drainage basins, and much of their morphology has been almost completely hidden by surficial processes. Radiocarbon tests indicate that some of the slide features are older than the testing limits, while other results range from approximately 18,000 to 40,000 yr B.P. The depth of erosion suggests that the paleo-slides may be as old as Pliocene. Geotechnical models of the paleo-slides, needed to analyze potential construction impacts, are developed from subsurface explorations, construction outcrops, radiocarbon testing, monitoring of geotechnical instruments, and geomorphology revealed by light detection and ranging (LIDAR). The process of predicting landslide boundaries (head scarps, toes, lateral and basal shear zones, etc.) for stability analysis of specific landslides has revealed details of their geologic evolution. This field trip provides background on (a) the investigations that have exposed numerous giant paleo-landslides, (b) findings and interpretations of the age of the landslides and (c) methods that are being employed to mitigate landslide reactivation.