There doesn’t seem to be different words in English for what in French we call a ‘lagune’ and a ‘lagon’. In English, we say ‘lagoon’ for both, so let me call the first a ‘land lagoon’ and the second an ‘atoll lagoon’ …
To remember while reading : this article was originally written in French for ‘baguette’ eaters and ‘bérêt’ wearers, then only translated to English. Thank you for your comprehension !
When you hear the word lagoon, you immediately think about sea and sand, but do you know what the difference between those two watery concepts is ? Can you describe a land lagoon and an atoll one, say what differentiates them ? No ? Well, voilà, voilà …
Land lagoons are beautiful
As for many of nature’s beauties, land lagoons are old, very old. Those that we can admire nowadays are all around 6,000 years old.
The Balos lagoon, in Crete, bordered by the Mediterranean Sea
© Olaf Tausch / Wikimedia Commons / CC-BY-SA 3.0
They were formed thanks to sand, pebbles, clay, silt, gravel and mud brought there by the waters of a river. Those alluvial deposits were carried from the continent to the ocean in a waterway and were then pushed back towards the shore by the ocean currents until it formed half a circle more or less open, or said otherwise, a beautiful beach.
For the pleasure of your eyes, here is a closed (land) lagoon, only connected to the Atlantic Ocean by a canal :
The Rodrigo de Freitas lagoon at the South of Rio de Janeiro
© chensiyuan / Wikimedia Commons / CC-BY-SA 4.0
And the third of those nature’s beauties that I selected for you is the famous Venetian lagoon (because you knew it was a lagoon, right ?) :
The Venetian lagoon between Italy and the Adriatic Sea
NASA Earth Observatory images [Public domain]
U.S. Geological Survey / Wikimedia Commons
But atoll lagoons are beautiful too !
Atoll lagoons look like land lagoons, but it’s not the same forces that give birth to them. They are generally formed in the very middle of an ocean around a volcano that, after having spitted out all the wrath of the Earth, sinks. Because yes, when a volcano is sinking, even very, very slowly, it makes the surrounding corals go up to the surface. For those who prefer visual explanations, here are three little drawings from the Dico Atlas des Mers et des Océans1. Please notice the red and green arrows :
Formation of lagoons
Dico Atlas des Mers et des Océans1 / Editions Belin
Illustration by Alexandre Nicolas
And thus here is the first of our lagoons, 3.6 kilometers diameter wide. Its emerged land spreads on 3.82 square kilometers and its lagoon strictly speaking (the big swimming-pool inside) on 12.6 square kilometers. It is situated in the South Pacific Ocean, midway between Australia and South America :
The Vahanga lagoon in French Polynesia
© NASA [Public domain] / Wikimedia Commons
Also right in the middle of the South Pacific Ocean in French Polynesia is the Raivavae lagoon. You can admire its 437-meter-high volcano in the middle. The island is 14.95 square kilometers.
The Raivavae lagoon and its volcano
© NASA [Public domain] / Wikimedia Commons
In the middle of the North Pacific Ocean this time, is located the atoll of Wake Island (the atoll, that is, the 6-kilometer-squared lagoon plus its surrounding coral reef that itself is 7.1 square kilometers). It is part of the territory of the United-States.
The Wake Island lagoon, in between China and Mexico
© Hohum, US Air Force derivative work [Public domain]
Wikimedia Commons / CC-BY-SA 4.0
A little summary so as not to forget anything
A little summary so as not to forget anything and for the little pranksters who only looked at the pictures …
– A land lagoon is formed by alluvion deposits pushed by waterways towards a sea or an ocean that pushes back those deposits so as to create magnificent beaches and bays. Land lagoons are situated on the coastlines of continents.
– An atoll lagoon is a stretch of water that is found inside a circle of land/coral reef after a volcano has made it emerge all around by getting old (sinking). Atoll lagoons are usually found in the middle of oceans.
And voilà ! Now, if at the turn of a path, you see a lagoon, you will not only admire the sight of it but you will also be able to appreciate the true value of the work of Mother Nature.
My resources to write this article :
1 Dico atlas des mers et des océans – Histoire, géographie et géopolitique, Pierre Royer, Editions Belin, avril 2013
Lagunes et estuaires sous l’influence de la marée (http://hmf.enseeiht.fr)