The term 'crumbling away' can be described as eroding, which is a seven-letter word. Erosion is the process of wearing away of the surface of the earth by wind, water, or other natural agents. It is a gradual process that can cause significant damage to land and structures over time. Erosion can also occur due to human activities such as deforestation, overgrazing, and construction. The effects of erosion can be seen in the form of landslides, soil loss, and coastal erosion.