How Did the Florida Keys Island Chain Form?

We love a trip down to the scenic Florida Keys, especially since there is so much to see and do. And, if you live anywhere in or near our luxury South Florida apartments, then they’re just a short hop, skip and a jump away at all times!

The Keys are such a special part of Florida and of the United States as a whole — there just isn’t anywhere else like it! But how did this unique environment form seemingly in the middle of nowhere? How did this little string of islands come to be home to some of the best reefs in the world? 

How did the Florida Keys form?

The Florida Platform

The story starts way, way back in time when the planet’s continents were smushed together to create the supercontinent Pangea. 

(“Smushed” is totally a scientific term, by the way.)

It all starts with the Florida Platform, a large platform that encompasses the Florida Peninsula and extends over 100 miles to the west of the modern shoreline in the Gulf of Mexico. It’s kind of like an iceberg in a way — the above-water-Florida we know today is just the tip of a much larger mass that exists underwater. 

In fact, if you were to look at a satellite image of Florida, you’d be able to see how this platform creates a relatively shallow sea before plunging violently into the deeper parts of the Gulf of Mexico. This large, underwater shelf upon which the above-water land sits is called the Florida Platform. 

Going back to Pangea, circa 200 million years ago. A lot was happening at this time, especially along the edge of the supercontinents Gondwana (composed of modern-day Africa, South America, India, Australia and Antarctica) and Laurasia (North America, Europe and parts of Asia). The grinding of tectonic plates and intense volcanic activity that created mountain ranges like the Appalachians also fused and separated landmasses from each other, and the then-above-water Florida Platform was right in the middle of it. In fact, it was actually originally attached to modern-day Africa, rather than modern-day North America! 

The violent collision of the two supercontinents fused the Florida Platform to Laurasia, and their equally violent separation caused the platform to rip right off Gondwana and travel away with Laurasia. 

What does this have to do with the Florida Keys? Well, the Florida Platform had a very different past than much of the rest of its newfound continental neighbor did, and it’s precisely because of its unique features that a place like the Florida Keys can even exist!

Once upon a time in the Ice Age

Let’s move forward in time a little bit and head over to the Ice Age — the last Ice Age, to be more specific. 

It’s around 2.6 million years ago and the North American continent finally looks a little more like it does today, for the most part. The Florida Platform has been almost entirely underwater throughout its attachment to North America, though a few hundred million years’ worth of sinking and rising seas have deposited layers and layers of limestone onto the platform.

Now, though, the Earth starts to enter the “Great Ice Age” in which massive continental glaciers formed over much of North America and Eurasia and caused sea levels to fluctuate all over the globe. 

Although the glaciers never reached as far south as Florida, the Florida Platform certainly experienced the effects of the chill. As the glaciers froze the planet’s water and dried out the globe, sea levels dropped significantly and exposed landmasses all over the world that had previously been underwater.

The shoreline of the Florida Platform rose and fell frequently in between glaciations during this ice age. When sea level fell, animals and foliage wandered onto the exposed land and erosion weathered the surface. When waters rose, the land would get covered with a shallow sea.

This back-and-forth went on for almost 2.6 million years and ended about 11,000 years ago, with the sea still slowly rising from the Earth’s last great glaciation.

Formation of the Florida Keys

Finally, we get to the good stuff!

It was during that time of rising and falling seas that the Florida Keys formed. The eastern edge of the Florida platform was shallower than the western edge and, as a result, is where most of the exposed land exists today. The southeastern edge of the platform was just the slightest bit deeper, though, and when sea levels were high, it spent a lot of time under a warm, shallow sea that was ideal for coral and marine life. 

Coral reefs built up along the southeastern edge of the Florida Platform each time the waters rose higher, creating a wall of coral reefs and limestone rock atop the already tall edge of the platform. As the waters sank and the reefs were exposed, erosion weathered down the coral and created limestone sand which, eventually, turned into sandy landmasses. 

Those sandy landmasses and coral reefs are exactly what make up our Florida Keys today. As the last Ice Age continued to raise sea levels, the long landmasses turned into a chain of smaller islands separated by rising seawater and surrounded by coral reefs. 

It’s a long, long story with origins further away than we could have ever realized, but the Florida Keys’ ancient history goes to show that this is an incredibly special place with value far beyond what we can see now. 

Florida’s coral reefs that created and still surround the Keys are millions of years in the making, yet they are experiencing a rapid decline due to human activity and climate change. The animals and marine life that call the shallow waters their home are at risk of extinction, just like the saber-toothed cats and mammoths that once roamed Florida’s exposed land during the Ice Age — though now it’s because of ocean acidification and overfishing. If climate change isn’t addressed, the Florida Keys may very well one day submerge below water once again, taking our national parks, roadside oddities and Conch Republics with it. 

Next time you’re near the Florida Keys or want to plan a trip to the many beautiful sights along the chain, remember how this little strip of land came to be and how amazing it is that we get to experience its beauty above the water, where it’s spent so little of its long, long, lifetime. 

Enjoy!

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Featured photo courtesy Pixabay/DayronV