These Square-Shaped Waves Look Strangely Beautiful – But They’re Actually Incredibly Dangerous

Image: via io9

Sometimes the real world is even stranger and more unearthly than the things we can imagine. That is certainly the case with these bizarre wave formations pictured off the coast of France in 2014. At first glance, you may think these images have been Photoshopped, but in fact they are examples of one of the weirdest natural phenomena on the planet.

Image: Ghrebaa

The grid shape you can see in the pictures is certainly not the result of some sort of artsy photo-trickery. It is actually something perfectly natural that can be explained with physics and math. Of course, that does not stop the photographic evidence from looking incredibly strange. And, despite their weird beauty, these wave patterns indicate great danger.

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Image: Phillip Capper

Swells in a body of water are created by the wind, but not in the way you might think. A swell is essentially a series of waves which are running in the same direction. But here is the key thing – swells are not created or altered by any localized wind. Indeed, the accumulated waves have their inception much farther afield.

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Image: James W Webb

Rather than being generated locally, swells are created by weather systems some distance away. The wind catches a large stretch of water, blowing it up into waves. These waves then travel away from the source that whipped them up, reaching great distances through the world’s seas and oceans. And it is due to traveling across such large areas that they take on a uniform appearance.

Image: Dion Gillard

Because swells have travelled so far, a lot of their original energy has disappeared. As a consequence, a lot of the randomness that might be seen in other types of waves has also been lost. It also means that the swells have a much smaller range of actual wavelengths than the waves that are created by wind from the local area.

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Image: McKay Savage

However, because swell waves tend to be mixed in with other kinds of similar sized waves, it is sometimes difficult for observers to tell them apart. That does not mean that it is impossible for sea watchers to discern the different kinds, however. Indeed, there are certain conditions where swell waves make themselves abundantly clear – and the results can be truly mesmerizing. One location in Western Europe enjoys the perfect conditions in which the cross-sea phenomenon can be easily witnessed.

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Image: via NASA

Île de Ré lies just off the West coast of France in the Atlantic Ocean. The island is a vacation magnet, thanks in part to its large stretches of sandy beaches. But it is not just the amenities that attracts the tourists. The island gets the same amount of sun every year as the popular South of France region, while a constant soft breeze keeps things just the right side of too hot.

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Image: Pline

The island is also easy to get around. Île de Ré is by no-means massive at roughly 19 miles in length and about three miles wide. The islet’s highest spot stands at just 72 feet above sea level. It is also easily accessible with a bridge connecting it to the French mainland. All of which are boons for those looking to top up their tan and take things easy. However, there is another reason why Île de Ré has been receiving attention in recent times.

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Image: Ghrebaa

And that is down to a number of natural factors which come together around the island to create the amazing effect seen in these pictures. It is called cross sea, and it happens when swell waves from two different weather fronts collide. And how cross sea comes about is incredibly interesting in its own right.

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Image: Pline

Because of the way sea swell is generated, and the distance that the waves travel, cross sea – or cross swell – can happen in even the calmest of waters. The winds that created the uniform pattern of waves may be hundreds of miles away, but the effect they have on one another is pretty incredible.

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Image: Martin Roell

The waves need to meet at just the right angle to create the amazing checker-board markings seen in these images. The two weather systems need to have been at oblique angles to one another. This allows the resulting waves to strike each other in what looks like almost perfect squares. Nevertheless, seafarers should not let this sensational display of nature lull them into a false sense of security.

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Image: cainadamsson

In fact, cross sea is one of the most dangerous conditions that boats have to face when they are out on large expanses of water. Studies have shown that a large percentage of maritime accidents on the world’s seas and oceans occur in a cross-sea state. And there is a very good reason why bigger vessels find such a situation so difficult to navigate.

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Image: alexatapsoft

The problem is that sailors find that boats can handle large waves much easier if they take them on at a 90-degree angle. And the merest look at the images of cross-sea conditions show that approach to be nigh-on impossible with waves rolling in from two different directions. But what can helmsmen do to try and minimize the effects of cross sea on their vessel?

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Image: via Rossnowlagh Surf Report

Alas, the simple answer to that question is “not very much.” The best course of action is to wait until one set of the waves has faded away. Although, obviously, that solution is not going to be much use if your boat is sat in the middle of the ocean. Swimmers don’t fare much better either. If you fancy a dip in the briny but observe a cross-sea state, your best bet is to avoid going in the water completely until it has passed.

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Image: Pline

There are certain factors which can dilute the spectacle of cross-sea conditions. For example, if cross-sea waves are hit by a strong local wind, there is a chance that the swell can be overrun by wind waves. This would break down the patterns, and mean that the cross-sea effect is much more difficult to discern.

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Image: via NASA’s Aqua/MODIS satellite

And then there is the sheer distance that the swells have travelled to consider as well. Because of the way that they are created, as we have seen, the waves gradually dissipate as they move over miles of sea or ocean. This can mean that by the time the cross-sea effect appears near land, the waves are so flattened that they are almost impossible to see.

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Image: W.carter

Finally there is the angle at which the waves intersect to bear in mind. If the weather systems that formed the swells have sent them out at similar angles, then when they meet they might look like they are coming from the same direction. Only when the intersection of the waves is at an oblique angle do these incredible patterns occur.

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Image: Andy Waddington

Even when all of those factors come together to create the optimum conditions for a cross sea, it is still possible to miss the effects of the phenomena. It is hard to visually define the wave shapes when observing from a beach level. To get the best view of a cross sea, the swell watcher needs to be elevated above the waves. Such as, for example, at the top of a lighthouse on Île de Ré.

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Image: Geof Sheppard

While conducive conditions do not occur all of the time, cross sea is nevertheless a spectacular show from the world’s seas and oceans. And one which a maritime lover should consider themselves lucky to witness. However, the force the waves generate can be more deadly than a riptide. So it is definitely a natural phenomenon that is best viewed from afar and not up close and personal.

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Image: G Travels

But, if you happen to be on Île de Ré, or a similar location where the conditions are ideally aligned, you could witness a display that almost looks out of this world. Nature always seems to have a way of showing off, and a cross sea is definitely one of the highlights. But bear in mind, it is unlikely you will be thinking that if one happens when you’re out at sea.

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