What is a cave, a crack/fault, an arch, a stack and a stump in geographical terms?
Caves form due to erosion (e.g. hydraulic action and attrition) causing cracks in a headland. These cracks expand due to the erosion listed before and freeze-thaw weathering, and eventually a cave is formed. Erosion carries on and eventually the back wall of the cave is eroded away to leave an arch. This arch is widened and when the pressure becomes too much the top collapses leaving a stack or a pillar of land standing out to sea, seperated from the headland. The sea continues to erode the stack, wearing it down until it becomes top heavy and the top of the stack collapses into the ocean. A stump is left. This is eventually eroded into nothing. An example of a stack is Old Harrys Rock.
