But if it blew for 48 hours, the wave’s crest would increase to 10.5 metres, about twice the height of a double-decker bus. Wind blowing for an hour at a speed of 55.6 kilometres per hour over a stretch of water 1000km wide would generate waves with a significant wave height of 0.7 metres. Oceanographers measure wave height using a term called “significant wave height”, which is the average height of the largest 33 per cent of waves in that region of ocean at the time. The height of a wave is determined by the wind strength, the length of time it blows and its fetch – the distance it travels over the water.
This causes the wave to stand up then pitch forward before eventually breaking. An analogy is a crowd of people doing a Mexican wave in a stadium: they stay in the same location, but the wave they create travels around the arena.Īs waves reach the shore, the shallow floor begins to run into their base, slowing their deeper parts. The rise and fall of water molecules creates a wave that moves in the direction of the wind.
Waves occur when the force of the wind blows over surface water, transferring its energy and causing the water to move in a circular motion. They are mainly caused by winds, and, if unimpeded, can travel for thousands of kilometres. There are many types of waves flowing across the oceans, from small ripples to huge walls of water, 30 metres high peak-to-trough.
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