The geosphere is the collection of physical and geological elements that contribute to shaping the Earth's surface. In the urban environment, the geosphere provides the foundation upon which population and infrastructure develop so that the elements of the geosphere affect them, but the population and infrastructure can also modify the geosphere. For example, urban development and even risk mitigation often involve excavations that interact with and often modify the underlying geology. Therefore, urban development requires an understanding of the local geology, such as soil stability, groundwater conditions, and subsurface characteristics. The geosphere includes the following elements: subsurface, soil, topography, resources, and hydrology.