- Wind blows over the ocean
- friction occurs
- energy is transferred ... creating waves!
Constructive..help to build beaches
long wavelengths and wave height less than 1 metre. Breaking waves have low amounts of energy and 'spill onto the beach'. The resulting swash is quickly absorbed by the beach & sediment thrown up by the breaking waves accumulates in ridges. Backwash has little power to move the sediment back towards the sea so the beach grows!
Destructive..remove sediment from beaches
Often the result of storms. Short wavelengths and high waves..lots of energy which cannot be easily absorbed by the beach. Strong backwash moves sediment back down the beach and eventually out to sea.
CLASSIFYING COASTAL ENVIRONMENTS & TIDES
STORM WAVE ENVIRONMENTS: frequent low pressure systems creating strong onshore winds which generate powerful waves. North-West Europe.
SWELL WAVE ENVIRONMENTS: less extreme patterns of wind and waves but a considerable swell built up over a long fetch, West Africa.
TROPICAL CYCLONE WAVE ENVIRONMENTS: extreme winds allowing huge waves to develop and push massive amounts of water towards coastal areas. South-east Asia.
TIDES: The alternative rise and fall of the level of the sea caused by the gravitational pull of the moon. High tides combined with events such as heavy rainfall causes catastrophic flooding.
STORM SURGES: high onshore winds & tides combine to give unusually high sea levels.