What is referred to as the steep surface at the top of a landslide, marking the upper slide surface?

The steep surface at the top of a landslide that marks the upper slide surface is called the head scarp. This feature generally represents where the ground has failed and begun to slide down the slope, creating a distinct and steeply angled surface. The head scarp is significant in understanding the dynamics and mechanics of mass wasting, as it indicates the point of origin of the slide.

In geotechnical and geological assessments, recognizing the head scarp is crucial for evaluating the stability of slopes and planning for mitigation measures. It is where the material has separated from the surrounding terrain, often providing insight into the type and extent of movement that has occurred during the event. The head scarp contrasts with features like fault scarps, which are associated with tectonic activity rather than mass wasting.