Saddle Island, located about halfway between Camden and North Haven, is perched atop a foundation of formerly molten basalt that, as it cooled, fractured in a distinctive geometric pattern. The stones that line the shore are actually the tops of multi-sided basalt columns or shafts that probably descend deep below the floor of the bay.
It’s difficult to judge just how far below the columns descend and we’ll never know how tall they were before erosion wore them down to their present length. We’d get a better idea of how deep they are if the columns were flexible like the bristles of a stiff push broom. Then, imagining we are giants, if we pulled our fingertips over the tops of the columns we’d see the length of the columns in profile. Thinking of the stones in this way, we get a better appreciation of what lies beneath what we see on the surface of Saddle Island.
An impressive example of the geological phenomenon that created Saddle Island is on the northeastern coast of Ireland, or the northern coast of Northern Ireland, depending on your politics. Here, an abundance of seemingly perfect hexagonal basalt columns or shafts emerge from the face of a tall cliff, looking like the bristles of a push broom. This multitude of pillars marches down the cliff face like an army descending the downhill track of a parabola that ultimately vanishes into the sea.
The area is so unlike any other part of the Irish coast that the spectacle looks man-made. Indeed, a legend says that long ago a giant named Finn McCool built a bridge of these columns, a bridge that spanned the Irish Sea and reached Scotland. It was the means by which Finn escorted a lady friend back to Ireland. But the bridge fell into disrepair and all that’s left of it is known as the Giant’s Causeway.
If Finn McCool did build a bridge it would account for the engineered appearance of the Giant’s Causeway, but two 21st century scientists suggest an alternative explanation for the phenomenon that created the Causeway and, by extension, our Saddle Island.
The April, 2002 Popular Science reported that scientists Eduardo Jagla and Alberto Rojo have solved the riddle of the basalt columns by creating an experiment that utilized not basalt but cornstarch. Their experiment is easily replicated in any science classroom. Jagla and Rojo combined equal parts of water and cornstarch and poured this mixture into a glass pie plate, creating a layer about a third of an inch thick. This dries for three to five days until there is an irregular crack pattern on the surface of the cornstarch. A round piece of cardboard is then laid on the top of the bed of starch and the plate is flipped over, releasing the starch patty from the plate. An examination of the bottom of the patty reveals a tiny but regular crack pattern that, when buckled, yields polygonal columns like those that created the Giant’s Causeway and are under Saddle Island.
Millions of years ago, where the Giant’s Causeway and Saddle Island are now, molten basalt welled up from deep inside the earth and created broad and deep lakes of basalt. Jagla and Rojo believe that as the molten basalt cooled, the surface cracked in an irregular pattern but as these cracks descended deeper they gradually took on a more geometric – hexagonal – pattern. This pattern tended to release the strain from the weight of the upper, cooler and more solid layers of basalt most efficiently. Efficiency is the same reason why honeybees make hexagonal combs. It’s the most efficient shape for their little bee bodies to fit into.
Keeping in mind that the columns appear in the lower level of the basalt lakes, we realize that the space where Saddle is today was once locked in the depths of a cooling basalt lake – until millions of years of erosion caused the sun to shine, finally, upon the acre or so of cold, hard basalt that now provides the island’s foundation. All of this took time, of course.
Randy Purinton, a frequent contributor to Island Institute publications, has now tiled his new bathroom floor.