Waves – Ripples in the sea caused by the transfer of energy from the wind blowing over the sea
The largest waves are formed when winds are very strong, blow for lengthy periods and cross large expanses of water.
Waves are caused by the transfer of energy from the wind to the sea (not to be confused with the tides which are caused by the gravitational pull of the moon and the sun, although this also does cause waves). As the wind blows over the surface of the sea it creates friction, forming waves.
The characteristics of waves are determined by the strength of the wind, its duration and fetch (distance it travels).
The stronger the wind, the greater the friction on the surface of the sea, and therefore the bigger the wave.
The size of a wave depends on its fetch. The fetch is the distance a wave travels, the greater the fetch the larger the wave.
In deep water, water molecules within a wave move in a circular movement. It is only in shallow water that the shore creates friction and turns the wave to break.
NOTE: Apart from wind (the main cause), waves are also caused by the gravitational pull of the sun and moon. This gravitational pull causes tides (literally the raising of large areas of the sea by gravitational pull), which result in tidal waves. Not so commonly, waves are also caused by underwater disturbances such as earthquakes, landslides and volcanic eruptions. These very big waves, called tsunamis, travel over the shore and can reach far inland.