Basics of Environmental Science

114 / Basics of Environmental Science

underlying deposit, in this case suggesting that a much larger river once flowed, probably fed by

glacial meltwater which also left a layer of till.

Soil is formed by processes at or very close to the surface. Once formed, it is affected by other

processes, some of which tend to transport it to new locations. The consequences of these processes

may be serious, catastrophic even, for humans living where they occur. In the central plains of

North America farmers from the east cleared away the natural prairie grassland and ploughed the

land to grow wheat in a climate drier and more prone to drought than that to which they were

Figure 3.11 Flood plain development from meander system

Figure 3.12 Modern soil developed over flood plain alluvium and glacial till