Deep-sea exploration

Deep-sea exploration is the observation and documentation of biological, chemical, physical, geological, and archaeological aspects of the ocean. Deep-sea investigation dates back to the Vikings, who used rudimentary instruments to measure ocean depths during their travels. Underwater technology saw major advancements during wartime eras, and vessels such as submarines allowed military leaders and scientists to investigate the ocean at greater depths.

The development of sonar in the 1900s dramatically advanced the field of deep-sea exploration. Sonar uses sound to detect the presence of objects far beneath the ocean's surface. Modern deep-sea instruments such as manned diving submersibles and robotic vessels provided additional ways for scientists to reach depths previously unheard of. Deep-sea exploration has led to many new discoveries of marine life and deep-sea ecology and shed light on a number of historical sea-related events.

Yet despite these achievements, much of the depths of the world's oceans remains unexplored. A common notion is that scientists know more about the surface of the moon than the deep ocean floor. While progress continues to be made, deep-sea exploration is a challenging endeavor that requires substantial resources, both financial and technological.

Overview: Early History

The ancient Greeks referred to the ocean's infinite depths as the abyssos, which meant bottomless. The English word abyss derives from this word. In the early days of ocean exploration, mariners attempted to measure sea depths with weighted lines called soundings. In 1521, Portuguese explorer Ferdinand Magellan lowered a 2,400-foot weighted line into the ocean to try to measure its depth, but the sounding never hit the bottom. This led Magellan to conclude that the ocean floor was unreachable and inhospitable. Explorers accepted this theory for many years before nineteenth-century scientists proved it wrong.

In 1868, Scottish naturalist Charles Wyville Thomson used deep-sea dredges to dig out underwater materials more than 14,000 feet below the surface. These samples revealed that life was present at greater depths, shattering previous theories claiming life was not possible below 1,800 feet. Spurred by these new findings, the Royal government initiated a landmark deep-sea study known as the Challenger expedition in 1872. A sailing ship called the Challenger spent four years measuring ocean depths with extensive soundings and collecting hundreds of water, sediment, and biological samples from every ocean except the Arctic. The journey covered more than sixty-thousand miles and is noted for giving scientists the first true understanding of seafloor structures such as the deep-ocean basins. The team also discovered more than 4,700 species of aquatic life and laid the groundwork for modern oceanography, which is the scientific study of oceans.

Wartime Oceanography

Oceanographic progress became an important wartime endeavor in the nineteenth and twentieth centuries. The US Navy wanted to gain strategic nautical advantages against its foes. It used submarines during the Civil War to sink enemy ships. Submarines were more widely used in World War I as a means of navigating the waters and observing enemy vessels. Wartime sea exploration led to the invention of sound navigation and ranging, later known as sonar. Sonar uses sound pulses to detect objects deep underwater by bouncing acoustic signals off the ocean floor. Sonar also measures distances this way by calculating the amount of time it takes for an echo to return to the surface. Deep-sea exploration experienced major advancements following the introduction of sonar. Canadian inventor Reginald Fessenden undertook one of the first acoustic explorations of the sea in 1914. Fessenden used sound pulses to detect icebergs ahead of ships. The military was also responsible for developing the magnetometer, which detected the presence of metal objects underwater. Magnetometers detected the metal hulls of enemy submarines, but also became useful for scientific measurements.

Military sea technology provided inspiration for a number of professional oceanographers. In 1934, two Americans set out to design a vessel that could dive deeper than submarines and had windows for viewing underwater life. Engineer Otis Barton and naturalist William Beebe designed a manned submersible vessel called a bathysphere and used it to plunge more than three-thousand feet into the ocean. The bathysphere allowed for first-person accounts of the sea life deep beneath the ocean's surface. French explorers Jacques Cousteau and Émile Gagnan took manned submersibles even further with the invention of the aqua-lung, the first commercially successful self-contained underwater breathing apparatus (SCUBA). SCUBA gear gave explorers firsthand access to the mysteries of the oceans, changing the course of deep-sea exploration.

Modern Progress

As underwater technology continued to improve, scientists gained a better understanding of Earth's structure. In 1955, crew members aboard the US Coast and Geodetic Survey ship Pioneer used a magnetometer to measure the magnetic field of the ocean floor. They discovered magnetic striping across the sea floor on the West Coast, with magnetic patterns of normal and reversed polarity spread throughout the seaboard. This discovery lent credence to the theory of plate tectonics, which describes the movement of the outermost section of Earth's surface and explains the emergence of mountains, volcanoes, and earthquakes.

Scientists used advanced instruments to resolve an array of oceanic uncertainties such as the thresholds of underwater environments and the location of famous shipwrecks. Underwater archaeologist Robert Ballard discovered hydrothermal vents in 1977. These vents made it possible for an ecosystem of deep-sea creatures to survive without the energy of the sun. Ballard's deep-sea investigations also led to the discovery of the Titanic wreckage in 1985.

By the 1990s, deep-sea technology gave scientists more access than ever before to the ocean's depths. Researchers used their knowledge to catalog the diversity, distribution, and abundance of life in the oceans. In 2010, a group of scientists from more than eighty countries released the Census of Marine Life, a ten-year research initiative dedicated to cataloging all known marine species into an online database. The census was the first ever of its kind and focused on improving scientific understanding of deep-sea organisms.

Advanced marine technology also provided comprehensive maps of the ocean's surface and floor. Scientists were now able to identify the deepest known point in the world's oceans, the Challenger Deep found nearly seven miles below the Pacific Ocean within the Mariana Trench. It was first visited in 1960 by explorers Don Walsh and Jacques Piccard in the bathyscape Trieste. Filmmaker and marine explorer James Cameron descended the depths of the Mariana Trench in 2012, becoming just the second manned expedition to reach the Challenger Deep. Cameron filmed his expedition and collected many samples from the bottom, which led to the discovery of several new subaquatic species.

Bibliography

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National Geographic. "Ocean Exploration: Timeline." National Geographic. National Geographic Society. Web. 17 Aug. 2014. education.nationalgeographic.com/education/media/ocean-exploration-timeline/?ar‗a=1#2

Ryan, Paddy. "Exploration of the Deep." Te Ara: The Encyclopedia of New Zealand. 12 June 2006, www.teara.govt.nz/en/deep-sea-creatures/page-1. Accessed 31 May. 2018.

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