Ireland’s bards and poets have long told tall tales of the epic Giant’s Causeway that protrudes out the coast of County Antrim, Northern Ireland. 

Legend tells of the Irish giant, Finn MacCool (or Mac Cumhaill in old Irish), a legendary warrior renowned for his wit and cunning, who, after starting a shouting match with another giant across the sea in Scotland, built the Causeway to cross the Irish Sea and give the potty-mouthed giant a bruising.

Today, the roughly 40,000 interlocking basalt columns are a major tourist hotspot — and they’re a stone’s throw away from where much of HBO’s Game of Thrones was filmed. 

Declared a World Heritage Site by UNESCO in 1986, it’s become a national treasure for the Northern Irish. It receives almost a million visits a year, and accessing the Giant’s Causeway is free of charge.

But how did it form? What phenomenon, natural or mystical, lies behind the strange hexagonal columns jutting out of the sea? Let’s find out.

What is the Giant’s Causeway?

It is located in County Antrim, around three miles from the town of Bushmills. It involves 40,000 interlocking basalt columns — most are hexagonal, although some have four, five, seven, or even eight sides. 

The tallest stands at 12 meters, plunging into the towering volcanic cliffs that rise 28 meters where the Causeway meets the land. 

Managed by the National Trust, the majestic and mystical site is one of the most popular tourist attractions in Northern Ireland. Indeed, since the Giant’s Causeway was announced to the world in 1693 following a paper published by the Royal Society, it’s gradually increased in popularity. 

However, long before science revealed the secrets behind the columns, legend, and mysticism surrounded this primordial rock formation.

The Legend of Finn McCool

Finn McCool is one of Ireland’s most legendary figures — a sort of King Arthur and Conan the Barbarian rolled into one. In most stories, he’s a normal human, but in the legend of the Giant’s Causeway Ireland, he rises to a staggering 54 feet tall.

Like all good legends, they change depending on who’s spinning the yarn. In the most popular and famous version, Finn gets into a shouting match with the Scottish Giant Benandonner, the Red Man. After Finn loses his “McCool” following the threats and abuse, he builds a Causeway with rocks from Antrim to go pick a fight.

However, when Finn reaches Scotland, he finds, much to his dismay, that Benendonner the Buggane is bigger and stronger than him. Never the fool, Finn hightails back to Ireland, losing a boot in the retreat — the “giant’s boot” can still be seen at the Giant’s Causeway today.

Unfortunately for our hero, Finn, Benendonner follows him home. Scared of the Red Man’s wrath, Finn’s Wife, Oonagh, pretends he’s a baby. When Benendonner visits, she says Finn is hunting, invites him to stay for food, and bakes Finn’s favorite bread but leaves the iron griddle inside, breaking Benendonner’s teeth.

Then, even more mischievously, she introduces the “baby.” Benendonner swiftly concludes from the baby’s size and the bread’s strength that Finn must be a colossal beast of a giant, a giant’s giant. 

Fleeing in terror, he races back across the Causeway, demolishing much of it. Finn throws a chunk of Earth that misses, supposedly creating the Isle of Mann. It’s a tall tale with little truth.

How was the Giant’s Causeway formed?

The real story behind it is even more cataclysmic. According to geologists, it formed when hot molten lava protruded through the Earth’s crust, slowly cooling into rock. Basalt, as it cools, fractures into columns at between 1,544°F and 1634°F. This phenomenon is known as columnar jointing.

Giant's Causeway

It’s estimated that it formed between 50 and 60 million years ago. Back then, tranquil County Antrim was a fiery hellscape of intense volcanic activity. Molten basalt erupted through chalk beds, forming a lake of lava. 

As the lake cooled and contracted, the Giant’s Causeway we know today was born. 

So, in a way, it was a titanic eruption of geological proportion that birthed this spectacular feature — just like the legends say.

Exploring Geological Wonders

Similar geological features, like Devil’s Postpile in the US and those near the village of Vik in Iceland, can be found globally.

Each location’s uniqueness is determined by the cooling speed, affecting the size of the columns.

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