How Are Waves Formed? The Anatomy of a Perfect Wave
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These days, we have surf reports, swell reports and surf forecasts that show us when and where we should be hanging ten next. Reasonably accurate online charts save surfers the hassle of deciphering complicated weather forecasts. However, the more you know about how waves are formed, the easier it is to predict the optimal surfing conditions all by yourself.
You don’t necessarily need to be a surfer to be fascinated with waves. All beach lovers are in awe of the ocean’s rolling waves, a trance-inducing sound and sight. But have you ever found yourself wondering how exactly waves are formed? Let me give you a hint – the wind is the very reason surfing exists in the first place.
So, what is it exactly that makes the ocean so restless, and how are great surfing conditions created? To help you understand this natural phenomenon, we’ll break down the anatomy of a wave, from how it is formed far out at sea to the way it breaks close to shore.
What is a wave?
Water does not travel in waves. Instead, waves travel through water. Does this sound confusing? Then let me break it down for you.
Water transmits energy, and waves are the result of energy passing through water. This energy is most often caused by the wind, but there can be other factors too, such as earthquakes, volcanic eruptions, landslides and even melting of Arctic ice caps. When not obstructed, this energy travels in oscillating movements on the surface of the ocean, sea or lake until it reaches the shore. Simply put, waves transport energy.
The most common types of waves that are found throughout the planet are produced by winds and are called wind-driven waves, or friction waves. These are the result of the friction between the wind and the body of water. When the wind blows on the surface of the ocean in a shorewards direction, it causes the water to move and produce a wave crest.
What is a swell?
When strong winds begin to blow on a stretch of calm water far out at sea, ripples are formed on the surface. These gradually turn into waves that make their way towards the coast.
A swell is a collection of waves produced by winds. Strong winds blowing hundreds of miles off the coast can produce some of the best waves on the planet, and surfers can’t wait to try their hands at them. However, sailors do not revere swells as they capsize boats.
When it comes to the quality of a swell, there are some variables to take into account:
- The wind’s strength – how fast it blows on the surface of the ocean;
- Duration of the wind – the longer it blows without interruption, the bigger and more powerful the waves will be;
- The wind’s ‘fetch’ –the surface of open water on which the wind blows in the same direction without hitting obstacles.
These factors influence the size of the swell and the wave period (the time in between successive waves). To this extent, there are two types of swell: windswell and groundswell. Let’s take a quick look at each of them:
Successive waves with short periods (10 seconds or less) in between sets are usually produced by local winds closer to shore. These waves are typically less consistent, weaker and sometimes even messy. Of course, that doesn’t mean you can’t find top-notch windswells too.
Wave periods of 13 seconds are the result of strong winds blowing farther offshore. These sets of powerful waves are known as groundswell, and are produced by longer-lasting winds and bigger ‘fetch’, which means that more energy is transferred into the water. The waves are of a far better quality and can travel long distances without losing their power.
How do you know when and how the wind is blowing?
Winds are formed when bodies of air move from a high pressure area to a low pressure one. You can find out where, when and in what direction the wind will be blowing by studying pressure charts.
Low pressure systems are associated with rainy weather and cloudy skies and are responsible for strong, quality groundswells. These mean strong winds that generate powerful waves, which can travel thousands of miles before reaching an obstacle (usually near shore). If these winds blow on the surface of the ocean for a longer period, the swell will get even bigger. If the wind blows on a greater area on the surface of the ocean (the ‘fetch’ we talked about before), the waves will be more powerful.
Image source: bbc.co.uk
So, what do you need to look for? Why, onions, of course! And no, not the ones that make you cry in the kitchen, although the ones I’m talking about will probably make you cry with joy too. The onions I’m talking about are used to describe deep low pressures on weather charts. Closely packed isobars mean strong winds, and they tend to resemble an onion when displayed on a pressure chart. If these isobars stay in one place for longer, the surf will be pumping.
Onshore winds blow from the sea towards the beach and tend to push in the direction of the wave, making it unstable. The stronger the onshore winds, the messier the waves will be – they break too soon, are less steep and usually mushy. If these winds get any stronger than 20mph (32kph), then the waves will most likely be unsurfable.
Wind blowing out to sea makes for optimum conditions, creating swell that is neatly ordered. Offshore winds produce waves that are strong enough to keep moving even in shallow water, forming steep faces before they break. They are fast, hollow and exciting to ride.
In many surfing spots, offshore winds occur in the morning and onshore in the afternoon.
The anatomy of a wave
We all know waves break, but do you know how? When waves travel through deep water without obstacles, they head to shore with a massive force. As soon as they reach shallow water, they slow down and their crest starts to grow. As with icebergs, the crest we see moving on the surface of the water is only a part of the wave, which actually extends all the way down to the ocean floor.
When a wave hits an obstacle, the lower part of the wave slows down, while the upper part continues to move, spilling over. Now, it is the way the wave spills over that surfers are interested in.
Photo by Duncan Rawlinson
There’s that one point when the wave tilts forward just enough, creating that sought-after shape of a rolling wave. This shape depends on the seabed – the steeper the seabed, the steeper the wave will be. Barreling waves, the holy grail of surfing, happen when deep water suddenly meets shallow water. When the transition on the seabed is smoother, gentler waves are formed, which are ideal for beginner surfers.
Depending on the seabed and direction of the swell, there are different types of waves:
Types of surf breaks
There are four main types of surf breaks:
- Beach breaks – the waves break over the sandy seabed. These are the best types of breaks for beginners to learn to surf. However, there are beach breaks in the world that can hold waves up to 20ft (6 m) tall. One such example is Hossegor in France.
- Reef breaks – the waves break over a rocky seabed or a coral reef. These are the classic waves you often see in surfing videos but can be quite treacherous if you happen to wipe out badly.
- Point breaks – the swell hits a rocky point at a certain angle, causing the wave to break along the shoreline. A good example is Bells Beach in Australia.
- Rivermouth breaks – the wave breaks over a sandbar formed by a rivermouth at the shoreline. Sandbars tend to change over time, which makes this surf spots rather unreliable.
Rights & lefts
Depending on the direction in which a wave breaks, there are left-hand and right-hand waves. Just remember that this is as seen from the surfer’s standpoint (i.e. out at sea, opposite from what you would see from the beach). Here’s an example: If a surfer is paddling towards a wave that is breaking from right to left, then the surfer must turn left to ride it. This is a left-hander.
Some waves peel in both directions starting from the same point. These are called A-frame waves, and can be surfed by two riders at the same time in different directions.
There are also waves that don’t break at all, break all at once or too fast to be surfed. These are called close-out waves, and approach the shore parallel to a straight coastline. These are usually unsurfable.
The gravitational pull of the sun and moon causes a periodic rise and fall of the water of the ocean. This can affect the surfing conditions in more ways that one.
First of all, tides can determine the shape of the seabed over which the wave will break. For example, a low tide usually means the wave will break in shallow water and will be steeper. Some spots are better to surf when there’s a high tide, some when there’s a low tide, and others on all tides, like the famous Spanish Left on Tenerife, Canary Islands. Secondly, an incoming tide (when the tide is on the rise) may help with the momentum of the waves, as it pushes in the same direction and supplies more power.
On average, there is a six-hour-and-12 minute period between low and high tide, but this can vary on certain coastlines.
Now that you know what you are surfing, head to BookSurfCamps.com, choose your next surfing trip and test the best waves on the planet!