In terms of depth and area, human interaction with the sea really takes place in the just the tiniest sliver of the oceans. The shallows, which disappeared altogether during the Ice Age, are really just coastal flats that happen to be currently underwater, like the shores of a river in spring when the melt water is running. The flooded edges of our landmasses are called the Continental Shelf; they can extend as far as 300 miles but on average they run out to around 50 miles offshore and generally the water is no deeper than 500 feet. This gently sloping extension of the beach compromises 8% of our oceans and 11% of the planet’s surface. Very little human activity will venture past the first third of this depth and surface users like swimmers, paddlers, surfers and even recreational divers, might as well be water bugs incapable of breaking the surface tension for as much of the entirety of the ocean they penetrate. Compared to the rest of the oceans the continental shelf is the miniscule playground of humanity; the kiddie pool.

If you could empty the ocean and stand at the deep end of the continental shelf, perched on the far edge of the shallows looking toward the deepest portion of the ocean we call the Abyssal Plain, you’d be staring down the steep wall of the Continental Slope. Climb down the contours of the slope and you’ve gone out an additional 10 miles from the shore and dropped 6500 feet (or 2000 meters) in elevation. From here things flatten out as the continental slope eases into the Continental Rise and as you move away farther and farther away from land you drop another 2000 meters. You have traversed the Continental Margin, that region between land and Abyssal Plain comprised of the Continental Shelf, Slope and Rise; combine all such regions on earth and you account for 15% of the surface our planet. Add the 30% of all landmasses rising above water and you are left with some pretty big gaps in the map, significantly more than half the planet, this is the abyss.

The abyssal plains aren’t much like terrestrial areas sharing the same name; they are interrupted by geologic features so fantastic that most people cannot even imagine them. The trenches and deeps begin at the 20,000 foot abyssal maximum depth then plunge down an additional 15,000 feet and we have barely glimpsed into them. The mid ocean ridges are the birthplace of the continents where mountain ranges are born in processes that unleash forces that are literally of a planetary scale, so powerful they continuously push entire continents away from each other. The black smokers in these geological nurseries may actually hold the answers to the riddle of life on Earth, but we are newcomers to these mystical gardens and what we have learned is far out massed by the exponentially multiplying questions any answers pose. The abyssal plain is truly the last frontier on this planet, the largest habitat on Earth and one that remains largely unseen by human eyes.

Humanity has constructed significantly more equipment that has gone into space than we have capable of surviving the crushing deep. The bathyscaph Trieste took two impossibly brave explorers to the bottom of the Challenger Deep, down to 35,000 feet, in 1962, over 50 years ago, one single time. They were there, resting on the bottom, waiting for the silt to settle, for about 20 minutes; less than one man hour. In contrast, since that dive another 12 unimaginably brave men have spent close to 600 man hours on the moon. This is fact: humanity has spent a thousand times more hours on Earth’s moon than in our own planet’s most forbidding, yet clearly accessible, places. But advancing technologies herald a new era; James Cameron recently became the third man to visit Challenger Deep and he will certainly be going back. His submersible and other new technologies capable of surviving the frigid depths are showing us more every day about the deeps. A technology leading the charge into the only remaining blank spots on Earth’s maps are Autonomous Underwater Vehicles; they are actually working to fill in those blanks.