The Sea Around Us

Rachel Carson's The Sea Around Us is a sweeping account of the world's oceans, covering their geological origins, physical dynamics, biological abundance, and significance to human civilization. The book synthesizes scientific knowledge from oceanography, geology, biology, and meteorology into a unified portrait of the sea as a force that has shaped the planet and all its life.

Carson opens by reconstructing the formation of the earth and its ocean. She describes the young earth cooling from a ball of whirling gases into a layered structure of molten iron, basalt, and a thin outer shell of granite. Before this shell fully hardened, the moon may have been torn away by a massive tidal wave of earthly substance, with the Pacific Ocean basin marking the resulting scar. Heavy clouds enveloped the cooling planet, and when temperatures dropped sufficiently, rains fell for centuries, filling the ocean basins and dissolving continental minerals that gradually increased the sea's salinity. In the warm primeval ocean, organic molecules assembled into self-replicating protoplasm, the material basis of life. The first organisms were simple microbes; when sunlight penetrated the thinning clouds, some developed chlorophyll and became the first plants, while animals arose by feeding on them. Over hundreds of millions of years, life grew more complex, yet the continents remained barren until the Silurian period, roughly 350 million years ago, when the first arthropod crept ashore. Carson emphasizes that all land animals carry the sea within them: Their blood contains sodium, potassium, and calcium in proportions close to those of seawater.

Turning to the living ocean, Carson describes the bewildering abundance of the surface waters. Through interlocking food chains, microscopic algae called diatoms support the entire ocean ecosystem: Tiny grazers feed on diatoms, small carnivores prey on the grazers, and the chain extends upward through schooling fish, sharks, squid, and great whales. These drifting communities are collectively called plankton, from a Greek word meaning "wandering." Carson draws on an account from the Norwegian explorer Thor Heyerdahl, who drifted 4,300 miles across the Pacific on the raft Kon-Tiki in 1947 and observed squid leaping from the water and enormous phosphorescent bodies appearing in the darkness. The sea surface is divided into zones defined by temperature, salinity, and nutrient content: Warm tropical waters produce tremendous species variety but fewer individuals per species, while cold polar seas sustain enormous populations of fewer forms.

Carson traces the seasonal cycle. In winter, cold, heavy surface water sinks and displaces warmer, mineral-rich bottom water, which rises to fertilize a spring explosion of plant growth. Diatoms multiply at astronomical rates, and plankton animals follow in matching numbers, turning the surface into a vast nursery for larvae of fish, crabs, and worms. Migratory fish return to their birth rivers. Summer brings giant jellyfish and vivid phosphorescence, while autumn sees fur seals migrating and toxic blooms of dinoflagellates, microscopic algae, along the Pacific coast, a danger known to Indigenous peoples for generations. Winter gales drive fish to warmer depths, but renewal is assured in dormant spores, hibernating copepods—tiny shrimplike plankton animals—and cod eggs rising through the cold water.

Carson then explores the deep sea, the least-known region of the ocean, covering roughly half the earth's surface in perpetual darkness. Only two people had descended alive beyond the range of visible light: the zoologist William Beebe and the engineer Otis Barton, who reached 3,028 feet in a bathysphere (a spherical deep-diving vessel) off Bermuda in 1934. In updated notes, Carson describes the 1960 descent of the Trieste to 35,800 feet in the Mariana Trench. The nineteenth-century belief that the deep sea was lifeless was disproven by discoveries of worms, starfish, and other strange creatures brought up from great depths. The most exciting modern discovery is the deep scattering layer, a vast living cloud detected by echo-sounding instruments in the 1940s that rises toward the surface at night and sinks during the day. Carson describes deep-sea creatures' bizarre adaptations: luminous organs, telescopic eyes, and elastic jaws capable of swallowing prey several times their own size. She also notes that the ocean is far from silent; hydrophones (underwater microphones) have recorded an extraordinary uproar of fish, shrimp, and porpoises near shorelines.

In her survey of the ocean floor, Carson identifies three geographic provinces: the continental shelves (shallow, sunlit, and biologically productive), the continental slopes (immense escarpments averaging 12,000 feet in height), and the deep-sea basins. The Atlantic Ridge, running 10,000 miles from Iceland southward, is part of a continuous mountain chain encircling the globe. She observes that undersea mountains, once worn below wave base (the depth below which waves no longer erode), enjoy virtual immortality compared to continental ranges. Carson describes ocean sediments as the most stupendous snowfall the earth has ever seen: an accumulation of eroded rock, volcanic dust, and the shells of countless organisms built up over hundreds of millions of years. From Atlantic sediment cores, scientists reconstructed four periods of glacial advance separated by warm intervals, reading the alternation of cold-water and warm-water microfossils as a record of climatic history.

Carson devotes attention to volcanic oceanic islands, tracing their life cycle from eruption through erosion and submergence. Krakatoa's 1883 explosion generated a hundred-foot wave, killed tens of thousands, and launched dust that produced spectacular sunsets worldwide for nearly a year. She examines how remote islands are colonized by wind and water, and documents humanity's devastating record of destroying island ecosystems through deforestation and the introduction of alien species.

Carson also examines the repeated advance and retreat of the sea across the continents throughout geologic time, driven by crustal movements and glaciation. During the Cretaceous period, about 100 million years ago, an inland sea 1,000 miles wide extended across North America. During Pleistocene ice ages, enormous quantities of water locked in glaciers lowered sea level, exposing continental shelves and creating land bridges that allowed migrations of animals and early humans.

Carson provides a comprehensive account of ocean waves, constructing the life history of a wave from birth in a distant storm through final breaking on shore and cataloguing waves' destructive power against coastlines. Her treatment of tides traces their cosmic causes and enormous local variation, from 50 feet in the Bay of Fundy to a foot or two at Tahiti. She describes the California grunion, which times its spawning precisely to the monthly tidal cycle, and closes with the flatworm Convoluta roscoffensis, which continues to rise and sink with tidal rhythm even in a tideless aquarium.

Carson examines the great permanent ocean currents, driven by winds, shaped by the earth's rotation, and modified by continental landmasses. The Gulf Stream carries warm water to northern Europe, keeping ports like Hammerfest and Murmansk ice-free. The Humboldt Current flows northward along South America carrying near-Antarctic cold, reinforced by upwelling (the rise of mineral-laden deep water) that sustains immense marine life. Carson explains how the ocean functions as a global thermostat and presents the Swedish oceanographer Otto Pettersson's theory linking approximately 1,800-year tidal cycles to climatic change. She also surveys the ocean's mineral wealth, from dissolved salts to petroleum, tracing oil's origin to the burial of marine organisms in stagnant, oxygen-free waters.

In a final chapter, Carson traces humanity's ocean exploration from the ancient Greeks' dread of a boundless sea through the voyages of the Phoenicians, the Greek explorer Pytheas of Massilia (about 330 B.C.), and the Vikings. She notes that Polynesian navigators had been crossing the Pacific for unknown centuries, guiding themselves by stars, ocean colors, and bird migrations. She highlights Matthew Fontaine Maury, who organized a worldwide cooperative system of navigational data while directing the United States Navy's Depot of Charts and Instruments, shortening ocean passages by weeks. Carson concludes by reflecting that while the surface is now largely known, the ocean's depths retain their mystery: "For all at last return to the sea—to Oceanus, the ocean river, like the ever-flowing stream of time, the beginning and the end" (204).