Scientific studies can identify landslide-prone areas and evaluate their risk. Large landslide complexes near Lewiston were identified by geological mapping. The slides formed along steep cliffs composed of basalt interbedded with sedimentary deposits. During the last ice age, catastrophic floods deposited gravel and sand on the tops of landslides and eroded the toes of slopes. These long-ago events may have triggered initial movements in the landslide complex. Between 1994-1998, a part of the slide directly below the Elks Lodge began to fail, threatening the building and temporarily blocking a major local road.