Stability of earth slopes and landslides belongs to one system. Landslide is the result of slope instability. Landslides occur in many parts of the world, especially in those areas with problematic soils and adverse environmental conditions. In analyzing the landslide problem, engineers and geologists often look at it from different points of view. The geologist regards landslides as one of many natural processes acting as part of the geological cycle. They are interested in only the ground movement with respect to the geological and hydrological features. On the other hand, the geotechnical engineer is interested in the soil types, their engineering behavior, the maximum height of the slope, and maximum slope angle in terms of a safety factor. In most cases, they do not understand the geological formation and environmental factors causing the landslide. Even within the engineering group, the practitioner often is interested in the measurements of soil-rock properties, ground movements, and environmental conditions; however, the theoretician is interested in the idealized failure surface in order to fit it into a mathematical model.