The three climatically controlled agents of erosion and transportation are wind, running water, and glaciers. These agents are distinguished by the fact that their work is governed by climatic conditions, unlike waves and ground water which are controlled by other factors.

These three agents represent the three states of matter — wind represents the gaseous state, running water represents the liquid state, and glaciers represent the solid state. This fundamental difference in their physical state influences how each agent erodes, transports, and deposits earth materials under different climatic regimes.

The work of these agents varies within any climatic region due to differences in wind velocities and directions, amount and kind of precipitation, its intensity, the relation between precipitation and evaporation, daily range of temperature, freezing and thawing frequency, and depth of frost penetration.

In contrast, the work of waves is not controlled by climate but by location along the interface of litho and hydro sphere — the coastal region. Similarly, the work of ground water is determined by the lithological character of the region, where karst topography develops only if rocks are permeable and soluble and water is available.