The publication of “Underworld: Journeys to the Depths of the Ocean” (Doubleday) comes on the heels of the disastrous last dive of the Titan, the submersible craft that imploded on June 18 while transporting passengers to view the wreckage of the Titanic. All aboard died, including the founder and CEO of OceanGate, the company that owned the craft. Underworld serves as both a wake up call to the unfathomable (pun intended) potential of scientific discoveries in the ocean’s depths, and as a counterbalance to the public’s impression (furthered by the reporting of the Titan disaster) that deep-sea excursions merely serve as adventure tourism for the wealthy.
A bonafide adventurer and bestselling author in her own right, author Susan Casey is well qualified to address the subject, and much more. In “Underworld,” Casey interweaves themes that delight, inform and caution readers concerning the discovery, complexity and challenges of undersea exploration.
But first, she offers some context: just how deep is deep? The author defines four zones of “deep” ocean (depths below 600’) used by undersea explorers — “twilight zone” (600’ to 3,300’), “midnight zone” (3,300’ to 10,000’), “the abyss” or “abyssal zone” (10,000’ to 20,000’) and “Hades” or “hadal zone” (20,000’ to 36,000’).
She notes that 36,000 feet is about 7,000 feet deeper than Everest is high, the principal reason so little exploration has occurred until recently. She notes that the lack of knowledge led to wild speculation about what lies below; the Carta Marina, a 16th century map, depicts a bottomless ocean populated by monstrous sea creatures. And for centuries thereafter the common wisdom was that the greatest depths of the ocean were bereft of all life.
Casey points out that the deep (below 600 ft.) ocean makes up 95% of the ocean’s volume, but that 80% of the ocean’s floor has never been mapped in detail. Modern submarines rarely reach the “deep” and, until fairly recently, the ability to go even deeper was limited.
She describes the two-mile descent of William Beebe and Otis Barton in June 1930 in a claustrophobic hollow steel sphere, 800 feet deeper than anyone living had ever gone, as the start of deep sea exploration and an inspiration for Casey’s own undersea journeys, beginning with a dive aboard the submersible Pisces V, a seven-foot, three passenger modern-day incarnation of the intrepid duo’s craft.
Casey informs us that bathymetry (the science of measuring seabed terrain) took a giant leap forward with the development of maneuverable submersibles, craft controlled remotely or by an on-board pilot. Some are capable of descending to the deepest reaches of the hadal zone, like the 35,876 foot Challenger Deep, located within the 1,000 mile long, 44 mile wide Mariana Trench. Through telemetry, human and video observation, and the ability to retrieve samples of minerals and specimens of sea life, submersibles are gathering prodigious amounts of data on what lies and lives below.
Her awe at the creatures she observes on her undersea journeys is palpable, as she describes the wonderful weirdness of rose-pink anemones, yellow sea stars, lilac purple octopuses. She also takes us beyond the exotic beauty: we meet some of the key players who make these ventures possible (including a hedge fund billionaire / explorer who financed a state-of-the-art submersible), and learn of the threat to aquatic life posed by pollution and undersea mining. We also learn of the woeful dearth of governmental funding: apparently images of people walking on the moon make for better optics than understanding the aquatic ecosystem that makes life on this fragile planet possible.
As she observes in “Underworld”; “Our survival depends on the ocean.” It’s a statement Susan Casey would like all of us to pay a bit more attention to.
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