With restless energies of the sun and heat of the earth, the biogeosphere circulates materials on which human life depends. In the global cycle of the earth, the slow rise of the land is balanced by steady erosion as soils and sediments return to the sea carried by the cycle of water. In Figure 1.1 the ocean on the left supplies the rain to the land on the right, and the water carrying sediments drains back to the ocean. In the original landscape before economic development, much of the water runoff passed through wetlands which captured the fertile soils and toxic substances. The filtered material in peaty sediments was eventually converted into coal by geologic processes.