Ontario Geological Survey the rock (bedrock); b) the deposits of sand, gravel, and till left by the glaciers; c) the mineral resources and potential; d) the energy resource potential within the rocks and soils; and e) the groundwater aquifers that contain groundwater resources. An understanding of what is at, and below, our feet is fundamental to human existence on the Earth, to understand the environment and habitats, and our ability to adapt to future changes, such as global warming. This geological knowledge is used to assess Earth resource potential, to attract investment, to ensure the health and safety of Ontario people from geo-hazards,
Internal erosion a larger cavity. The process continues until the formation of a sinkhole. It is possible for a cavity to not collapse; this will lead to backward erosion occurring. Soil contact erosion can occur between any granular layer and a finer soil such as in silt-gravel, and often results in a loss of stability, increases in pore pressure and clogging of the permeable layer. Experimental results show that close to the geometrical limit, the point at which the fine particles can "just pass" between the coarse particles(the filter criterion), erosion initiation and failure are much more likely. It is possible to