Groundwater sapping is the geomorphic process whereby groundwater exits a bank or hillslope laterally and erodes soil from the slope. This often causes the slope to be undermined and undergo mass wasting, hence the word sapping. This is one of the processes involved in the formation of gullies, such as lavaka. Surface of the Earth Geomorphology is the study of landforms, including their origin and evolution, and the processes that shape them. ... Groundwater is water located beneath the ground surface in soil pore spaces and in the fractures of geologic formations. ... Severe soil erosion in a wheat field near Washington State University, USA. Erosion is the displacement of solids (soil, mud, rock, and other particles) by the agents of wind, water, ice, movement in response to gravity, or living organisms (in the case of bioerosion). ... Soil is material capable of supporting plant life. ... In geology, mass wasting is the process by which rock and regolith move downslope. ... Sapping, or undermining, was a siege method used in the Middle Ages against fortified castles. ... A gully is a geological feature that is created by running water such that it forms a deep ditch. ...