Image courtesy of Wikimedia Commons.
The Giant's Causeway is a four-mile stretch of columnar basalt at the northern tip of Ireland. It was given its name in the folklore called the Fenian Cycle, or Ossianic Syble, an oral tradition of 800 or 900 years' duration that was finally put into writing in the 12th and 13th centuries. By legend, Oisin (Ossian) was the son of a great king, the giant Finn MacCool (MacCumhaill), leader of the Fianna warriors in the 3rd century. Orra Hitchcock referred to his epic poetry in her remark on the wildness of Scottish scenery.
One legend explaining the geological formation says that Finn MacCool became so enraged by his counterpart in Scotland, the giant Finn Gall, that he tore rock out of the cliffs and made a bridge across the water in order to chase him. When he finished the bridge, he was too tired from the exertion to pursue his foe, so he lay down to sleep in a large crib. Meanwhile, Finn Gall found the bridge and crossed over to Ireland, but at the sight of what appeared to be an enormous baby in the crib, became terrified at the thought of how large the father must be and went running back to Scotland, ripping the bridge to pieces behind him so he couldn't be followed.
The Causeway formed about 60 million years ago, when tectonic plates breaking apart allowed lava to shoot out and begin to cool. Fractures formed at the surface during the cooling process and continued to form as the cooling continued downward. The columns are five, six, or seven-sided, with a few having four or eight sides, and are up to 82 feet tall. The slower the cooling, the greater the diameter of the column would be. Those at the Giant's Causeway are from 15 to 20 inches in diameter.
Altogether, there are approximately 40,000 columns in three sections: Grand, Middle, and Little. The most spectacular are the Middle Basalts, vertical columns with narrower, irregular columns on top.
Because the feature is on the coast and reaches down into the sea, it appears to be a bridge to Scotland's island of Staffa, in the Hebrides, where similar columnar basalts are found in Fingal's (Finn Gall's) Cave.