How Islands Form – Three Rooker Bar on Florida’s Gulf Coast
Islands form in a number of ways. Some are born overnight while others take decades or even centuries to form. How islands are formed depends a great deal on where the island is located. Islands in coastal regions will form as sandbars while those in volcanic areas will form from rock and lava. Islands are classified in three broad categories – continental, oceanic, and tropical. Continental islands form a part of a larger continental shelf, much of which might be submerged below the surface of the oceanic. Oceanic islands are not part of a continental shelf and are most often formed by volcanic activity. Coral reefs form many tropical islands.
In the 1970s Three Rooker Island didn’t exist. The 1.5 mile stretch of sea where it now rises was nothing more than shallow water, and an occasional sandbar between Honeymoon Island to the south and Anclote Key to the north.
It didn’t rise from fire and smoke like the new volcanic islands we often hear about in the news or see on YouTube. There was no roiling water, no smoke plumes in the air, no land formation overnight.
Instead, Three Rooker Island slowly emerged like a languid cat waking from a nap. Local currents deposited sands in one place, having taken them from another. In the 1980s, it was a solid sandbar, the youngest member of West Florida’s barrier islands. There is now an even newer one, called North Anclote Sandbar, to the north of Anclote Key. And others forming along channels like the one below at the mouth of the Anclote River.
Sandbars come and go, appearing and disappearing at Mother Nature’s whim. Some remain and become Barrier Islands, one of the most prevalent types of islands in the US, especially along the Eastern Seaboard and Gulf Coast. These islands, like Three Rooker, most often form as shifting currents pile sediment in one place. Hurricanes and tropical storms create, or destroy, others. Barrier Islands protect approximately 15% of the world’s coastlines, and though they are most often associated with more southerly latitudes – think Florida, Georgia, the Carolinas – they can form nearly anywhere, such as Germany’s Norderoogsand.
Thirty years after its formation, Three Rooker is a well-established island. Grasses and trees grow on it. About three quarters of the island is a protected bird rookery. And about one-quarter of it is open for human enjoyment. This doesn’t mean the island doesn’t change. It does. In the past three years a channel has split the island into North and South Three Rooker. Its semi circular shape is more elongated some years than others. But for now, it looks like Three Rooker is here to stay, another link in the chain of islands that buffers the West Coast of Florida.