Eleuthera is a long, thin island in the Bahamas primarily known for its rolling pink sand beaches. But it's what can be found on the island's narrow, cliff-sided northern stretch that brings scientists to this tropical paradise: two giant boulders that bizzarely sit some distance from the cliff edges.
Boulders are a strange thing to see on such a small, narrow island. What's clear is that they could not have formed where they sit, and that some immense force would have had to have placed them there. Now an international team of researchers think they may have solved the mystery, but their explanation foreshadows an ominous climate future, reports Phys.org.
Although there are large rocks strewn all across a thin region of island known as the Glass Window Bridge, it's the two largest boulders, affectionately named "cow" and "bull," that seem truly impossible. The predominant theory so far has been that the boulders were placed where they currently sit by a raging superstorm some 100,000 years ago, when sea levels were much higher than they are today. But the new research calls that idea into question.
It turns out, it wouldn't have taken a superstorm. Using computer simulations, the researchers found that waves moving at just 20 to 25 mph would have had enough energy to push the two boulders, each weighing 383 and 925 tons respectively, from where they formed on a lower cliffside. Waves with that kind of power formed during Hurricane Sandy, in 2012.
Sea levels would have had to have been 20 to 30 feet higher than they currently are to submerge the boulders adequately to move them, but that means that as sea levels continue to rise due to global warming, this is the kind of thing we might see again on islands like Eleuthera, as they become inundated by storm surges. Of course, climate change will also mean that more intense and more frequent boulder-moving storms are on the horizon.
The research was published in the Proceedings of the National Academy of Sciences.