‘Megastorms’ That Throw Thousand-Tonne Boulders Over Clifftops May Be On Their Way Back Thanks To Global Warming
Standing atop a 60-foot cliff overlooking the Atlantic, James Hansen — the retired NASA scientist sometimes dubbed the “father of global warming” — examines two small rocks through a magnifying glass.
Towering above him is the source of one of the shards: a huge boulder from a pair locals call “the Cow and the Bull,” the largest of which is estimated to weigh more than 1,000 tons.
The two giants have long been tourist attractions along this rocky coast. Perched not far from the edge of a steep cliff that plunges down into blue water, they raise an obvious question: How did they get up here?
Compounding the mystery, these two are among a series of giant boulders arranged in an almost perfect line across a narrow part of this 110-mile-long, wishbone-shaped island.
Hansen and Paul Hearty — a wiry, hammer-slinging geologist from the University of North Carolina at Wilmington who has joined him here as a guide — have a theory about these rocks.
It’s so provocative — and, frankly, terrifying — that some critics wonder whether the man who helped spawn the whole debate about the dangers of climate change has finally gone too far.
The idea is that Earth’s climate went through a warming period just over 100,000 years ago that was similar in many ways to the warming now attributed to the actions of man.
And the changes during that period were so catastrophic, they spawned massively powerful superstorms, causing violent ocean waves that simply lifted the boulders from below and deposited them atop this cliff.
If this is true, the effort kicking off in Paris this week to hold the world’s nations to strict climate targets may be even more urgent than most people realize.
Hearty, an expert on Bahamas geology, first published in 1997 the idea that Cow and Bull were hurled to their perch by the sea.
Since then, Hansen has given the work much added attention by framing the boulders as Exhibit A for his dire view of climate change — which has drawn doubters in the scientific community.
But as Hansen examines the rocks on a recent morning, Hearty explains some of the evidence.
In particular, Hearty points out that the tiny grains that constitute the boulder rocks are more strongly cemented together and less likely to crumble than other rocks nearby, a sign that the boulders are older than what’s beneath them.
While there is a suggestion in the scientific literature that the boulders were simply left behind after surrounding rocks eroded away, Hearty and another leading Bahamas geology expert, Pascal Kindler of the University of Geneva in Switzerland, agree that the boulders are older than the surface upon which they rest and, thus, probably were moved by the sea.
Even the tourist placard near here takes their side, saying the ocean “lifted them atop the ridge.” But exactly how it could have done that is another matter.
Scientists have tended to attribute odd boulders such as these to tsunamis — there’s little doubt they have the power to move large rocks.
One recent study found that in the Cape Verde islands, 73,000 years ago, a 300-foot-high mega-tsunami carried boulders as large as 700 tons atop a cliff almost as high as the Eiffel Tower.
But more recent studies have also attributed large boulder movements to storms. And now into the fray has stepped Hansen, who, in 1988 testimony before Congress, put the climate issue on the map by contending — correctly, as it turned out — that global warming had already begun.
If he is also right about the boulders, Earth could be in for a rough ride.
And even if not, one thing is clear: Cow and Bull present a scientific mystery whose solution may serve as a reminder of just how violent and dynamic a planet we live on.
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