The term subsidence refers to geological events which cause the surface of Earth to shift. This may result in sinkholes, landslides and ground heave. Subsidence insurance can be included in your homeowners' insurance policy, either as standard or for an additional cost. When moving into a new home, an assessor should evaluate the risk of subsidence to determine whether you require subsidence insurance. Houses built on land with high concentrations of limestone, for instance, have a much higher risk of suffering subsidence than houses built on harder ground. This is due to dissolution of limestone which occurs when underground water supplies erode the stone, causing caves which can result in subsidence. Mining, seasonal rainfall, tree planting or removal, extreme drought and geological faults can all cause subsidence. Initial signs of subsidence occurring include cracks and bulges in walls, sticky doors and windows and ripples appearing on wallpaper.