As terrestrial creatures, our perspective on our environment tends to be highly land-oriented. As perpetually adventurous creatures, we love to discover and rediscover the world. We live on a primarily aquatic planet with oceans we love to live near and to travel across, but the mystifying and intimidating vastness of the world beneath makes much of our world into a world apart.
In a recent post we considered how bodies of water are often simplified in cartography because the detailed features of the land tend to matter a lot more to us. We also thought about differently water might be understood in maps if our inhabitation of the environment were different. Our perception of a place can change as the focus shifts away from the land and its inhabited cities, to the subaquatic features that are normally hidden from our view. When we make this shift of focus, we can better understand the geographical relationship between the land above sea level, and the land below. In this map series we'll explore the Straits of Florida, the stretch of water between the land masses of Florida and Cuba that connects the Atlantic Ocean and the Gulf of Mexico.
We're going to start with the city-centric orientation we're used to seeing on maps, and steps out into the water until we reach a fully bathymetric focus. However, we'll keep a visual on three key cities: Miami, FL; Key West, FL; and Ciudad de Habana (Havana), Cuba.
Above Sea Level
In the first map, we can learn about where the urban areas are in the parts of south Florida and central Cuba shown. In Florida, the most developed places are along the west and east coasts of the peninsula, facing the Gulf of Mexico and the Atlantic Ocean, respectively. Miami is the most populous metropolitan area in south Florida, and the entire region is popular for its tropical climate and scenery, and vibrant culture. But a massive portion of the southern tip of Florida remains almost completely undeveloped and sparsely populated, being dedicated instead to the Everglades National Park, Big Cypress National Preserve, and smaller reserve areas. These areas are extremely important to the regional ecology and to Florida's water quality. To the east of Miami we can see a small portion of the Bahamas.
A little further south is a string of islands connected one after the next by US-1, which runs along the eastern coast of the US all the way from the tip of Maine until it ends in Key West, the southernmost populated area in the nation. US-1 is the only way to enter or leave the Keys by car. Some of the keys are very small or frequently flooded, while others are home to considerable populations. Being so far-flung into the midst of the sea, and rising so little above sea level, the Keys are highly vulnerable to storm events. If you look closely, you can see a couple of land forms beyond Key West, which are unpopulated natural reserve areas.
The distance from Miami to Key West is about 130 miles or 210 km, and from Key West to Havana is about 100 miles or 161 km, separated by the Florida Straits. Cuba has a network of highways connecting major cities with smaller towns interspersed pretty evenly, with many bays and small islands called "cayos," the Spanish term for "keys," along the north and south coasts. There are several significant natural preserves, the most sizable being Parque Nacional Ciénaga de Zapata. Cuba has a strong cultural influence on Miami and other south Florida cities.
Water Features
These areas are framed by the Atlantic Ocean, the Gulf of Mexico, and the Caribbean Sea, with the Florida Straits stretching between. This first map shows us the names of many cities and towns, and shows the highways running between them, but the water is still a flat blue plane. Let's take our dive and see what's under the surface of the water. Click to enlarge.
Underneath the flat blue plane, we can see a lot of new information. Turns out the planet below sea level is as full of variety as the world above sea level! Now we can start to understand familiar land formations not just as "the world," bounded by the seas, but as the portions of land formations that extend above the surface.
The lighter blue areas are the "shelf" or more elevated regions; the darkest areas, in the midst of the Straits of Florida and extending toward the Atlantic Ocean, are the deeper regions known (ominously) as "abysses;" the moderate shades in between are "slopes" between the shelves and abysses; and underneath we can see shaded terrain providing more detail about the surface of the sea floor. The next map is similar, but breaks the information down further. Click to enlarge.
Consider the legend as a guide. We can now see the hills and plains of the abyss, and the high, medium, and lower portions of the shelves. Notice the difference in underwater geography to the west of Florida versus the east. The shelf in the Gulf of Mexico drops off not far beyond the Keys, giving way to sloping and then abyssal areas. The drop-off is much more immediate in the Atlantic coast near Miami. The Florida Keys and the many Cayos along the coasts of Cuba are no longer floating specks of land, but the uppermost reaches of shelf areas. They are connected with one another under the surface.
Notice also the somewhat triangular shape toward the eastern part of the map. Before, we could see a few tiny islands too small to have names. Now we see an entire landform, the edges of which are slightly ridged enough to protrude above the surface. Imagine if it were higher, or the sea were lower. It would be an island with a name and probably inhabitants! Do you think it would be part of Florida, or part of Cuba? An independent nation, or part of the Bahamas?
How different would the world be if even one of the landforms people live on was too low in elevation to breach the surface? If Florida was a subaquatic plateau hiding under the flat blue plane, I guess it would just be part of the Straits of Florida. Although they'd probably be called something else.
An Unknown World
We're only scratching the surface (pun intended) in all there is to learn about the subaquatic geography of this area. It's almost like another planet. The bathymetric elevations, the geological composition, the currents and the wildlife may be beyond the scope of today's map series, but there's more for us to discover. Let's dive a little deeper and look at how some of the geographical features are classified. Click to enlarge.
The information about seafloor geomorphology is from GRID Arendal (2014), a project by P. T. Harris et al. to digitally map the features of the entire seafloor. Here is a link to read more from their research project, Geomorphology of the Ocean. We'll refer to their definitions to understand the features.
Consider the legend again to understand the shapes demarcating subaquatic features, and look at the previous maps to compare them to the texture of the terrain. In dark blue are "canyons," the steep-sided, deep valleys with a V-shaped cross-section, comparable to canyons or gorges cut by rivers through land. The "terraces" in light blue are relatively flat areas with steep slopes on either side. This is slightly different from the "plateau" in yellow, a large and relatively flat area which drops off abruptly on one or more sides. Think of the difference between a hill with a level summit, and a desert plateau. In dark gold there is a "rise," defined as a feature near a continental formation with a thickness greater than 300 meters and a smoothly sloping surface.
In bright blue are "escarpments," are "linear, steep slope[s]" between more shallow sloping areas, outside of a shelf. Other kinds of features can coincide with escarpments. A "basin" like the one in purple on the west edge of the map is a depression, or a decrease in elevation, confined to a defined area. These are the features indicated by information from P. T. Harris et al. for this part of the world, but the list of defined seafloor formations is much more extensive.
Think of how you feel when you see a map of Mars or the Moon. A strange blend of the familiar and the alien. We can see a lot of features that are similar to the world we know, making it easier to understand. Mountains and valleys, rifts and vantage points, as excitingly diverse as the geography above sea level where we live. But there are unfamiliar characteristics too, and the sunlight lands in a different way. We don't see the plants and animals we know. It's fascinating to think that the world underwater actually is the same planet we know, and that so much of it is hidden from us.
Coming Up for Air
Now take a moment to flip back to where we started, when we could see all the information about our terrestrial civilization, our city names and roadways and boundaries. This is the way most maps present the world, and with good reason, because this is where our lives happen. Whether for navigation or education purposes, the land is where our interests normally lie. But when we bring the seafloor terrain into the picture we gain a sense of context for the geography of the places we call home, and the world gets a bit bigger.
We see a version of the earth that doesn't have cities and towns set up across it, or any of the structures and lines we use to assemble civilization. Although it's earth, somehow it isn't anyone's home. And although it isn't home, it's home anyway -- the foundation that all lands rise from. Humans gravitate toward the water and depend on it. And by sometimes peeling back the flat blue plane like we've just done, we can envision the sea as a real place that humanity needs to take responsibility to care for, not an unlimited food supply or a receptacle for waste, but a gigantic and complex part of our world that will always be interconnected with our own quality of life.