The Mariana Trench

The Mariana Trench is a long, crescent-shaped cavern deep in the Western Pacific Ocean. It lies just east of its namesake Mariana Islands near Guam, north of Australia and south of Japan, and contains the deepest known points on planet Earth. Follow along as Tidbits explores some interesting facts about this amazing oceanographic phenomenon.

BY THE NUMBERS

• The Mariana Trench stretches 1,580 miles in length, more than five times longer than the Grand Canyon, and averages about 43 miles wide. The depth of the ocean here is 5,960 fathoms, or about seven miles straight down.

• The first depth measurements in the Mariana Trench were made by the British survey ship HMS Challenger, which was used by the Royal Navy in 1875 to conduct research in the deep cavern. The greatest depth that they recorded at that time was 26,850 feet (8,184 m), measured by dropping a weighted rope overboard.

• In 1951, another Royal Navy vessel, also named the HMS Challenger, returned to the area and discovered an even deeper location in the trench with a depth of 35,760 feet (10,900 m) determined by echo sounding. This exceptionally deep part of the trench was named the Challenger Deep after

the vessels that made these measurements. The Challenger Deep area of the Mariana Trench is the deepest point in all of Earth’s oceans, at 36,200 feet (11,034 m) below sea level.

• By comparison, most ocean life lives above a depth of 660 feet. The deepest a human has ever scuba dived is 1,090 feet. Nuclear submarines travel at a depth of about 850 feet. Whales are rarely seen below 8,000 feet. The depth of the sunken Titanic is 12,467 feet.

ORIGIN AND FORMATIONS

• The Mariana Trench is located where two tectonic plates collide, with the Pacific Plate being forced downward into the mantle underneath the Mariana Plate. This subduction zone forms the trench. Although there are other trenches in ocean floors across the planet, this is the deepest. That's because it’s in the middle of the ocean where there are no rivers nearby constantly discharging mud and silt to fill the trench. The Pacific plate is also comprised of dense volcanic rock which is very heavy, weighing the ocean floor down further.

• At that extreme depth, the immense water pressure is about 1,100 times higher than the normal atmospheric pressure on shore. At approximately eight tons per square inch it is roughly equal to a column of 100 elephants balancing one atop another on a single postage stamp. Exploration is challenging because that much extreme pressure causes normal instruments to literally implode.

• Because of the rift in the ocean floor, there is much undersea volcanic activity at that location. Lava that once spewed from these volcanoes formed the curved chain of the Mariana Islands which exactly mirrors the arc of the Mariana Trench.

• One such undersea volcano spews liquid carbon dioxide from thermal vents that look like cone-shaped chimneys. The liquid emitted from these chimneys is 2170F (1030C). Another submerged volcano oozes a pool of molten sulfur, a phenomenon seen nowhere else on earth.

• Other volcanoes vent hydrogen sulfide which feeds a specific type of bacteria, which feeds specialized microbes, which in turn feeds fish.

LIVING CREATURES

• Recent scientific expeditions have discovered surprisingly diverse life in these harsh conditions. Animals living in the deepest parts of the Mariana Trench easily survive in complete darkness under the extreme pressure.

• One of the most common organisms at the bottom is called a xenophyophore, which is a type of giant single-celled amoeba. They eat by surrounding and absorbing their food. These giant-sized amoebas can reach four inches (10 cm) in diameter. Another is the... READ THE REST OF THIS INTERESTING COLUMN HERE (for FREE, of course):