31 Brantley, Susan White, Tim 2005 At Earth’s surface, a complex suite of chemical, biological, and physical processes combines to produce soil from bedrock within the zone that extends from the outer<br /> limits of vegetation to the lower limits of groundwater (the Critical Zone; Figure 1). This weathering engine transforms primary minerals, provides nutrients to nourish<br /> ecosystems and human society, mediates the transport of toxic components within the biosphere, creates water flow paths that shape and weaken bedrock, and<br /> contributes to the evolution of landscapes at all temporal and spatial scales. At the longest time scales, the weathering engine sequesters CO2, thereby influencing the<br /> global carbon cycle, long-term climate change, and weathering rates.<br /> Despite the importance of soil, our knowledge of the rate of soil formation and related processes (Figure 2) is limited because the weathering zone forms a complex,<br /> ever-changing interface, and because scientific approaches and funding paradigms have not promoted integrated research agendas to investigate such complex<br /> interactions. No national or international initiative has promoted a systems approach to the investigation of weathering science across the broad array of geology, soil<br /> science, ecology, and hydrology.