The next chapter deals with another wave, the tide. It is an often misunderstood phenomenon. The currents chapter looks at the atmosphere first and how sunlight passes through to warm the surface. On its way, various atmospheric gases filter the sunlight and also Earth's outgoing radiation. More about this will be discussed in the chapter on global warming.
Solar radiation varies with latitude, but particularly with depth in the ocean.
Heat is distributed from the warm tropics to the cold poles by means of air and water circulation. A major influence on the movement of air and water is the Coriolis force, explained in detail. The chapter ends with deep water currents. Where the sea meets the land, often dunes and beaches are formed. In the chapter about these, it is explained how beaches and dunes form and how they interact with wind and waves.