Regolith materials cover over 85 per cent of the Australian continent and range from thin, skeletal, soils over slightly weathered bedrock through to very highly weathered bedrock at depths of more than 100 metres below the surface. Important geological and biochemical cycles operate within the regolith zone, including groundwater systems and nutrient cycles involving carbon, nitrogen, oxygen, phosphorus and sulfur, and all elements necessary for life and the biomass. Biogeochemical cycles within this zone are complex and occur across diverse spatial and temporal scales. Northern hemisphere researchers use the term ‘critical zone’ to describe this life-sustaining environment. Critical zone research involves integrated studies of water with soil, air and biota in the near-surface terrestrial environment (Lin 2010)
