Geography

Bermuda [1] lies at 32°17’ N, 64°46’ W, along the latitude of Savannah, Georgia. The nearest point of land is Cape Hatteras, North Carolina, 590 miles to the northwest. Roughly the size of Manhattan, Bermuda is 2,100 miles west of the Azores and 910 miles north of the Bahamas. There are no distinct topographical regions on the island, but rather, a variety of natural habitats, which can be found in most of the nine parishes.

Bermuda consists of a limestone cap sitting at the pinnacle of a submerged volcanic seamount. Its geological origins can be traced back 110 million years to the Mid-Atlantic Ridge, a volatile, mostly submerged division between the divergent American and European tectonic plates. Scientists believe “Mount Bermuda” was the byproduct of a massive volcanic eruption just west of the ridge, which moved slowly westward over the next 80 million years. A second eruption caused the volcano to enlarge into the Bermuda Seamount, incorporating a trio of peaks: the Bermuda Pedestal (on which the island now sits), the Challenger Bank, and Argus Bank. Of these, only the 13,000-foot Bermuda Pedestal now extends above sea level. The seamount moved a further 500 miles west in the following 30 million years, leaving the island currently situated in a stable area of the earth’s crust.

The seamount’s limestone cap was formed biologically over the last million years as seaweeds, algae, corals, and other shallow-water marine organisms laid down deposits. A 350-foot-deep layer of calcium carbonate was formed, and as sea levels fell, this was exposed to air, about 100,000 years ago. The result was the formation of many tons of sand, which wind blew across the island to form rolling dunes that eventually hardened into what geologists term “Aeolian” limestone, meaning “created by wind.” Remnants of these old dunes, sometimes even dunes atop dunes, can be seen along the shoreline of Bermuda or in road cuts such as the dramatic Blackwatch Pass in Pembroke [2]. Soft, porous limestone rock now makes up Bermuda’s entire surface and has been quarried over the centuries for roof slate and building blocks used for Bermuda’s characteristic island homes.

The porous nature of the limestone helped shape Bermuda’s geological identity. It allowed rain to soak into the surface rock, deterring freshwater runoff that would have created streams, rivers, and lakes. Instead, rainwater burrowed deep into the earth, forming a network of twisting underground tunnels, caverns, and caves, which still honeycomb certain parishes and give Bermuda one of the highest concentrations of caves in the world. Some are found underwater, becoming refuges for rare species. In the best known, you can find stalactites and stalagmites, columns, flow stones, and soda straws.

Bermuda’s biological history begins about 800,000 years ago—the date of the oldest terrestrial fossils, belonging to a petrel (a tube-nosed seabird), found in Hamilton Parish [3]. But climatic changes and the dramatic rise and fall of sea levels over time created havoc for the habitats, animals, and plantlife that may have lived on an ancient Bermuda far larger than its current form. As Canadian research scientist Dr. Martin Thomas points out in his book, The Natural History of Bermuda, observations from deep-ocean submersibles examining the Bermuda Pedestal have revealed former beaches at a depth of 315 feet—a fascinating clue about the island’s previous life. It was not until about 10,000 years ago that rising sea levels stabilized and Bermuda took its present shape. Marine and terrestrial organisms then arrived as larvae, spores, or adults, transported by wind or carried on debris propelled by the powerful Gulf Stream. Against big odds, these first forms of life would slowly spawn the rich environment to which Bermuda is home today.