Abstract This chapter treats two areas of the northwestern United States characterized by great late Cenozoic outpourings of basaltic lava. The western part of this region is underlain by flood basalt of the Columbia River Basalt Group. As discussed below by Waitt and Swanson, this area constitutes the Columbia Plain. The laterally extensive, thick cooling units of the Columbia River Basalt Group contrast with the thinner, less extensive flows of the Snake River Plain, which lies to the southeast. Lavas of the Snake River Plain were emplaced coincident with Pliocene-Quaternary rifting, from about 5 Ma to present. Much of the Columbia Plain is overlain by tens of meters of Pleistocene loess, which is extensively dissected to form the rolling topography of the Palouse Hills. In the northeast, broad channels were carved into the Palouse loess and underlying basalt by cataclysmic Pleistocene floods. The characteristic flood erosion of the basalt impressed early settlers as a scaring of the earth by removing its protective soil, and the term “scabland” was applied to it. The best known geomorphic studies in the Columbia Plateau centered on the role of cataclysmic flooding in the origin of its landscape. The central figure in this research for over half a century was J Harlen Bretz (Fig. 1), a glacial geologist at the University of Chicago. Bretz (1923a) used the name “Channeled Scabland” to describe the area of loess-mantled northeastern Columbia Plain that was scoured by flood channels. In 20 major articles and monographs, mostly published between

Abstract: Investigations of the role of sea level in producing coastal erosion have focused mainly on the long-term rise due to melting of glaciers and thermal expansion of sea water. There are, however, additional shorter term changes in the local sea level produced by a variety of ocean processes. Variations in the coastal currents, for example, can alter the water level at the shoreline due to the geostrophic balance between the current and the offshore sea-surface slope. Other factors which may alter local sea level include changes in atmospheric pressure, winds blowing either in the longshore or cross-shore directions, and the occurrence of upwelling. Because the inclined continental shelf and slope act as a wave guide, the fluctuations often become trapped and propagate over longshore distances beyond where they are actually generated. In that many of these processes are typically seasonal, the responding sea level also has a pronounced seasonal cycle, but frequently there can be significant fluctuations at periodicities of several days to a few weeks. The magnitudes of such changes vary considerably with coastal location but are typically on the order of 10 to 30 cm, achieving a maximum of about 100 cm in the Bay of Bengal. The occurrence of an El Niño in the equatorial Pacific is known to have considerable impact on the erosion of the coasts of California and Oregon. This occurs because associated with an El Niño are shifts in the storm paths and a temporary rise in sea level. An El Niño is a breakdown of the normal equatorial wind and current patterns. This breakdown releases water which is normally set up in the western Pacific by the trade winds. The release creates a “wave” of sea-level rise, which first propagates eastward along the equator and then poleward along the eastern ocean margin. Such “waves” have been measured in the tide records of the western United States, amounting to some 20 to 60 cm and lasting for several months. Such transient sea-level changes have likely played an important role in coastal erosion.