Mariana Trench

How low can you go?

The Mariana Trench is located in the Pacific Ocean, just east of the 14 Mariana Islands (11″21′ North, 142″ 12′ East) near Japan. As you probably already know, it is the deepest part of the earth’s oceans and the deepest location of the earth itself. It was created by ocean-to-ocean subduction, a phenomenon in which a plate topped by oceanic crust is subducted beneath another plate topped by oceanic crust.

How deep is it you ask? The maximum known depth is about 6.825 miles! Although it’s the deepest point in the world’s oceans, Mariana Trench is not the part of the ocean floor closest to the earth’s core, a result of the earth not being a perfect sphere.

On the ocean floor of Mariana Trench, there are hot water vents that emit minerals such as hydrogen sulfide[1] which feed the barophilic bacteria[2] that feed microbes that in turn feed the ocean’s fish. Temperatures at the bottom range from 34°F to 39°F, and it is considered to be one of the world’s coldest places.

The deepest part of the Mariana Trench is the Challenger Deep, so named after the exploratory vessel HMS Challenger II; a fishing boat converted into a sea lab by Swiss scientist Jacques Piccard. The trench was first sounded during the Challenger expedition in 1875, using a weighted rope, which recorded a depth of 26,850 feet.

In 1951, Challenger II surveyed the trench using echo sounding, a much more precise and vastly easier way to measure depth than the sounding equipment and draglines used in the original expedition. During this survey, the deepest part of the trench was recorded when the Challenger II measured a depth of 35,760 feet.

Four manned descents and three unmanned descents have been achieved. The first was the manned descent by Swiss-designed, Italian-built, United States Navy-owned bathyscaphe Trieste[3], which reached the bottom at 1:06 pm on January 23, 1960, with Don Walsh and Jacques Piccard on board.

This was followed by the unmanned remotely operated underwater vehicles Kaikō in 1996 and Nereus in 2009. The first three expeditions directly measured very similar depths of 35,768 to 35,814 ft. The fourth was made by Canadian film director James Cameron on March 26, 2012. He reached the bottom of the Mariana Trench in the submersible vessel Deepsea Challenger, diving to a depth of 35,787 ft. Other descents have followed.

The deepest part of the ocean is called the abyssal zone. it is host to thousands of species of invertebrates and fish including such oddities as the Angler Fish, so-called because it uses a bioluminescent protrusion to attract its prey.

The Challenger Deep in the Mariana Trench is very cold and highly pressurized; its floor features hydrothermal (hot water ) vents formed by spreading tectonic plates which release hydrogen sulfide and
other minerals which are consumed by the barophilic bacteria are then consumed by other microorganisms, which are in turn, consumed by the fish, and so on.

The temperature around the vents can reach up to 572° Fahrenheit. The venting fluid is highly acidic, while the water from the deep ocean is slightly basic. Although the venting fluid is prevented from boiling due to its dissipation into the surrounding freezing water, creatures from the deep show an incredible resistance to temperature extremes by having different proteins which are adapted for life under these conditions;

allowing the animals to eat, process food, and reproduce. The ocean floor at such depth consists of pelagic sediment, also known as biogenous “ooze”. Pelagic sediment is composed of shells, animal skeletons, decaying microorganisms, and plants; it is generally yellowish and very viscous. At least 22 trenches have been identified although not all are classified as major. Of this number, 18 are in the Pacific Ocean, three in the Atlantic Ocean, and one in the Indian Ocean.

The pressure there is 1000 times that of the sea level’s atmospheric pressure with the average sea-level pressure being 1013.25 hPa (29.921 inHg; 760.00 mmHg). Giant amoebas were discovered in Mariana Trench in 2011 by Scripps Institution of Oceanography scientists. These giant amoebas can reach 4 inches in diameter. Research suggests that the trench is approximately 180 million years old and is considered to be one of the oldest seabeds in the world. A 16-pound heavy spherical ball would take 36 minutes to reach the bottom.



Footnotes
  1. Hydrogen sulfide is a chemical compound with the formula H2S. It is a colorless chalcogen-hydride gas, and is poisonous, corrosive, and flammable, with trace amounts in an ambient atmosphere having a characteristic foul odor of rotten eggs. Swedish chemist Carl Wilhelm Scheele is credited with having discovered the chemical composition of purified hydrogen sulfide in 1777.
  2. Barophilic bacteria grow preferentially or exclusively at moderately high hydrostatic pressures
  3. The first bathyscaphe, the FNRS 2, was built in Belgium between 1946 and 1948 and was damaged during the 1948 trials in the Cape Verde Islands. Substantially rebuilt and greatly improved, the vessel was renamed FNRS 3 and carried out a series of descents under excellent conditions, including one of 13,000 feet into the Atlantic off Dakar, Senegal, on February 15, 1954. A second improved bathyscaphe, the Trieste, was launched on August 1, 1953, and dived to 10,300 feet in the same year. In 1958 the Trieste was acquired by the United States Navy, taken to California, and equipped with a new cabin designed to enable it to reach the seabed of the great oceanic trenches. Several successive descents were made into the Pacific by Jacques Piccard, and on January 23, 1960, Piccard, accompanied by Lieutenant Don Walsh of the U.S. Navy, dived to a record 35,814 feet in the Pacific’s Mariana Trench.

Sources

The Mariana Trench
National Geographic
Wikipedia
RobotSpaceBrain
Fireup Facts


Author: Doyle

I was born in Atlanta, moved to Alpharetta at 4, lived there for 53 years and moved to Decatur in 2016. I've worked at such places as Richway, North Fulton Medical Center, Management Science America (Computer Tech/Project Manager) and Stacy's Compounding Pharmacy (Pharmacy Tech).

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