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Home > Ocean > Exploring the Deep > History of Undersea Exploration

History of Undersea Exploration

Since the beginning of time, humans have had a love affair with the sea. The bounty of the sea has given up countless scores of fishes that have fed families the world over for thousands of years. Explorers have braved its waters to discover fertile new lands and untold riches. But the sea has also been feared, seeming to “swallow” entire fleets of ships and taking hundreds of lives without a trace. For many thousands of years, the sea was considered a watery desert, robbing men of their sanity, and families of fathers, brothers, and husbands. The sheer darkness of its depths made it impossible to see into them and gain a glimpse of what lay beneath. The fear of what lay in the unknown depths won out over curiosity, so that exploration of the waters beneath the surface was never considered necessary or reasonable. Occasionally, ocean travelers saw glimpses of deep creatures that would rise to the surface to display their horrific and bizarre proportions. Such strange and mysterious creatures gave rise to many legends of sea monsters, reason enough for people not to consider venturing into the dark and dangerous abode of the deep.

But with the advent of the Industrial Age, fear gave way to growing curiosity. Wealthier nations were heady with the strength of their new technologies, instilling in them a sense of power and invincibility. No longer feeling like victims of circumstance, highly developed societies, fat from the wealth of their burgeoning industrial waistlines, were bent on conquering nature. This new sense of courage and curiosity gave rise to early expeditions seeking to remove the veil of mystery that lay beneath the waves. Early explorers attempted to plumb the depths of the ocean and discover, once and for all, just how deep the depths really were. The tools that were used to try to fathom the deep were as simple as a cannonball or large steel weight, fastened to the end of a long hemp rope that was lowered into the water until it touched bottom. This proved to be an imprecise and unreliable method for measuring incredibly deep water and many of the early soundings (as these measurements were called) came up with some depths that have since been corrected. Since then many scientific expeditions have brought back data and specimens that reveal a more complete picture of the undersea world. One of the earliest and most thorough scientific expeditions undertaken to map the sea and catalog its unknown life forms was conducted by the British naval ship, the HMS Challenger.


The HMS ChallengerCommissioned by the British Royal Society, the Admiralty, Treasury and Museum, the HMS Challenger was a naval corvette ship that had been essentially stripped of its weapons and fitted with every modern scientific instrument of that time. In December of 1872, the Challenger set sail with 240 scientists, sailors, and crewmen on the most ambitious and comprehensive study of the sea to date. The purpose of the three-year long expedition was to thoroughly explore and catalog the entire depth of the sea all around the world.

At the time, the increasing interest in Charles Darwin’s Theory of Evolution had spawned tremendous curiosity about the nature of life underneath the sea. Early philosophers and thinkers, aided by the anectodal evidence of sea travelers, theorized that the very deepest regions of the sea maintained such inhospitable conditions, that no life could possibly exist there. Known as the Azoic Theory, this thinking began to come under increasing scrutiny when some exploratory missions by the British Royal Society had dredged up incredible numbers and diversity of life forms from depths as far as three miles down. Many of the bizarre organisms that were brought to light had never been seen before, except in the fossil record. It seemed that the deep harbored creatures from earth’s distant past and the search for living fossils began in earnest.

Darwin’s Theory of Evolution, that biological diversity and the evolution of species was a result of adaptations to the continually changing environment, breathed life into the idea that the deep sea should harbor living fossils. It was felt that the conditions of the deep sea should be as a time capsule, with relatively little or no change over the course of geologic time. This unchanging environment was thought to maintain conditions favorable to the UN-evolution of species – such that creatures dwelling in the depths of the sea millions of years ago might still exist in modern times, where they lay undisturbed and undiscovered by man. The slurry of throwback lifeforms that had been previously dredged up was evidence that pointed to the possibility of living fossils.

Over the course of the three-year journey, the Challenger crew made some groundbreaking discoveries that revealed a much more detailed and thorough picture of the mysterious abode beneath the waves. For the first time, a clearer picture of the shape of the sea floor began to emerge. For thousands of years, it was thought that bottom of the ocean was a vast, unbroken plain that was flat and shapeless. But after hundreds of soundings taken in oceans around the world, it was discovered that the sea floor was not flat at all. In fact, an incredibly long, unbroken chain of mountains rising up from the sea floor, what is now known as the Mid-Atlantic Ridge, was discovered. Some of the undersea mounts rose up to just a mile beneath the sea, looming over a mile high from the sea bed. Detailed soundings taken around coastlines revealed long, gently sloping shelves radiating out from shore, which then abruptly dropped off to the deep sea floor, what are now known as continental shelves. Some of the soundings that were taken were so incredibly deep, far deeper than any other place in the sea, that these narrow bands of exceptionally deep undersea terrain became known as trenches. It was discovered that the majority of the sea bed consisted of a vast, relatively flat plain just over two miles deep, which they called the abyssal plain. At the conclusion of Challenger’s voyage it was clear that the ocean was not at all a bottomless, featureless domain. The picture that emerged was one of a complex sea floor that seemed to be a world unto itself, shaped by unknown forces.

After more than three years at sea, the Challenger had dredged up from the depths 4,717 new forms of life never before seen by human eyes. Slimy, smelly creatures with grotesque and nightmarish features, such as extremely long, daggerlike teeth, enormous, bulging eyes, and body parts that gave off their own bluish-green light (bioluminescence), were regularly dredged up. Some creatures that surfaced in Challenger’s trawling nets were throwbacks to earlier evolutionary time periods and seemed to be missing links between creatures found in the fossil records and modern ocean dwellers. Just about everywhere in the sea, all around the globe, at even the deepest of depths, the Challenger’s trawls and dredges continually came up with numerous life forms. It seemed even the coldest, darkest, and most inhospitable regions of the deep sea were easily occupied by incredibly diverse species that were well-adapted to life in the depths. The Azoic Theory of lifeless regions of the deep sea had finally been laid to rest.

William Beebe and the Bathysphere ->


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Deepest Place in the Ocean

Abyssal Plain
Continental Shelves
Submarine Canyons
Coral Reefs
Sea Mounts
Mid-ocean Ridges
Volcanic Islands
Deep Ocean Trenches


Anaconda vs. Piranha
Challenger Deep
Colossal Squid
Deepest Fish
Goliath Tarantula Hunt
Great White Shark

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