The Pacific Ocean houses the Marianas Trench, the lowest point on Earth.
The deepest regions of the oceans occur at the ocean trenches, chasms in the ocean floor with high pressures, low temperatures and minimal light conditions. In 1960, oceanographers Jacques Piccard and Don Walsh explored the deep ocean in the Trieste, a submarine vehicle designed to withstand the hostile conditions of the deep sea. Intent on investigating the oceans' deepest point, the Marianas Trench, which lies 11,000 meters beneath the Pacific Ocean off Japan's coast, the explorers observed a fish swimming in a region long thought to be devoid of life. These two scientists have remained the only humans ever to attain these depths.
Description
Water covers more than two-thirds of the surface of Earth. The average depth of the oceans measures about 4 km, but the trenches, appearing as long, vast chasms dug into the surface of the ocean floor, stretch thousands of fathoms beyond the ocean floor. These features can reach as far down as 11 km, eclipsing even the height of the highest mountain on Earth, Mount Everest, which measures 9 km in height. Extreme conditions in the ocean trenches, or hadal zones, force creatures that inhabit them to survive pitch darkness, frigid temperatures and brutal pressures.
Conditions
Twenty-two of the 26 better-known ocean trenches occur in the Pacific Ocean alone. Pressure decreases 1 atmosphere, the force exerted by air on objects at sea level, for every 10-meter descent in water. The pressure at the lowest point in the oceans could surpass 1,000 times the pressure you experience on land, able to crush conventional submarines like aluminum cans. Because sunlight cannot penetrate beyond the upper 1,000 m of water, the trenches reach near freezing temperatures, and the surroundings are bathed in complete darkness.
Creation
The same subterranean movements that cause natural disasters such as earthquakes, volcanic eruptions and tsunamis also formed the Earth's surface, giving rise to all landforms and sea features. The surface of Earth comprises a series of puzzle pieces, called tectonic plates, which join together at different boundaries. Plates edge away from one another in divergent boundaries, move closer together in convergent boundaries and slide against one another in transform boundaries. Convergent movement of the plates lining the ocean floor created the ocean trenches; plates wriggled underneath other plates, creating gashes kilometers deep in the ocean floor.
Ecological Dynamics
Because of the lack of light at the ocean's lower levels, food becomes scarce in the trenches. Food chains and food webs almost everywhere begin with producers, organisms such as plants and algae that make their own food. All other creatures within the food chain rely on producers, either directly by consumption or indirectly by consuming those organisms feeding on the producers. Other trench animals have adapted a scavenging lifestyle, living off the remains of dead organisms that fall from the upper levels of the ocean. Predatory animals that feed on these scavengers have evolved characteristics that allow them to maximize feeding opportunities.
Life in the Trenches
More than 40 years after the Trieste's dive, Alan Jamieson, a researcher at the University of Aberdeen's Oceanlab, released the Hadal-Lander, an unmanned exploratory vessel, into various ocean trenches. Pictures brought back to the researchers revealed that life in the trenches included fish, shellfish, snails, sea cucumbers, worms, starfish and the shrimp-like amphipods. Fish such as the rat-tail living in the ocean trenches appear less bizarre than fish such as the fangtooth, which occupies waters that run less deep.
Tags: ocean floor, ocean trenches, Pacific Ocean, deep ocean, lowest point
