Giant Icebergs Used to Ram Up Against Florida

21,000 years ago, icebergs carved up the ocean floor off the Miami coast

Photo: Matthias Kulka/Corbis

Gaze out to sea from Florida's beaches circa 21,000 years ago, and you would have spotted not paragliders and sailboats on the horizon but icebergs. According to a new study, icebergs from the Hudson Bay's Laurentide ice sheet—a massive sheet of ice that all but covered Canada—broke free and drifted down the eastern coast of the landmass that would one day become America. 

Sometimes those icebergs would make it as far south as Miami and the Bahamas. Those giant hunks of ice—some of them up to 1,000 feet thick—left deep gouges along the Florida coast that can still be measured today. 

Researchers from the University of Massachusetts, Amherst, built a computer model of the icebergs' movements after gathering measurements from around 400 trenches the drifting blocks left on the seafloor, from Cape Hatteras in North Carolina to Florida. The icebergs, they found, were "enormous." As the researchers pointed out in a release, "Such icebergs are only found off the coast of Greenland today."

Florida, the team writes, was a very different place back then. At times, due to meltwater events, the water was "only a few degrees above freezing." But as the Atlantic's City Lab points out, this doesn't mean that there was "a constant parade of icebergs along the coastline." Instead, the team determined that icebergs most likely only broke free from the Hudson during extreme floods. When that happened, however, icebergs could pepper the waters off the Florida Keys for up to a year. 

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