With the help from the National Science Foundation, the University of North Carolina at Wilmington, and others, the researchers reviewed a millennium approximately 120,000 years ago when temperatures were slightly warmer than today, Earth’s glaciers had melted, and the world’s sea levels were almost 30 feet higher. The scope of the period of the study ruled out tsunamis, said Hearty.

The researchers concluded big waves and wind pushed boulders, rocks, sediment, and other materials from the ocean almost six miles inland on the islands in what were probably epically violent storms.

They looked at boulders as heavy as 1,000 tons that were once underwater but now sit on land that was dry before they arrived, so-called “chevron storm ridges,” or V-spaced lines of sediment pushed inland by rushing water and deposits of beach sedimentation almost 100 feet above sea level.

“Super perfect storms,” said Hearty.

Especially helpful for the research were ooids – or tiny grains of calcium carbonateand other materials plentiful off the islands that quickly harden like cement when out of the water. Layers of cemented ooids are called oolite. One can see oolite layers at many road cuts in the Bahamas and Bermuda, with each one providing a perfectly preserved record of the conditions that created it.

“Every steep road cut that would go over the top of the island, we would look closely and essentially see beach bedding,” said Hearty.

In the paper, Heart and his co-author described the oolite as “a message from the past; a glimpse into the future.” But he said it’s a future humankind can avoid if people took action to combat carbon pollution and climate change.

“We’re tinkering with the dials of global climate and we are already seeing that things are happening,” he said. “The story is clear and unambiguous. We are messing with things that are bigger than us.”