The Mariana Trench is the deepest point known on Earth. However, it is not a narrow crevice as its name implies. It is actually the location of a subduction zone.
These occur when a part of the ocean floor slips beneath a neighboring portion. In this case the Philippine plate submerged the Pacific plate. Subsequent tectonic activity prevented one from lying flat on the other, and caused them to penetrate vertically into the Earth’s interior at steep angles.
A tectonic plate is a massive rock, 60 miles or thicker according to Robert Stern, a geophysicist at the University of Texas, Dallas. It sinks into the earth bending down in gentle undulations.
The Mariana Trench is the deepest point on Earth because the Western Pacific is made up of some of the oldest seabed in the world — over 180 million years old. It was formed by lava from underwater volcanic action. As lava cooled, aged and spread it became increasingly dense and settled.
Two other factors make the 1,580-mile-long Mariana Trench unfathomably deep. It lies far from landmasses and muddy river deltas carrying sediment that would have raised its level. Moreover, neighboring fault lines cut the Pacific plate into long grooves, allowing it to bend more steeply downward than at other subduction zones.
Marine biologists and scientists recently plumbed the Mariana Trench that gave up a creature living in this deepest point on Earth – a snailfish that is so new it does not yet have a name. The discovery was made during a marine voyage on board the research vessel Falkor of the Schmidt Ocean Institute.
The 30-day voyage is considered to be the most comprehensive survey of the world’s deepest areas ever undertaken. The team was actually looking for and collecting core geological and ecological samples when this wholly unexpected visitor swam past their camera.
The Hadal Ecosystem Studies (Hades) team sent unmanned landers to varying depths from 16,404 to 34,777 feet under the sea. They were attempting to get a handle on the ecosystems at different levels in the ocean’s hadal zone. They studied the steep surrounding walls of the undersea canyon.
Most expeditions concentrate on the Challenger Deep (the deepest part of the trench). Dr. Jeff Drazen co-chief scientist from the University of Hawaii likens it to studying a mountain ecosystem from the summit alone, a very limited perspective.
The deep end is merely a landscape that is barren and level. The sides of the trench are of much more scientific interest, hiding many of the secrets of the deep. Dr. Alan Jamieson, from Oceanlab at the University of Aberdeen, said that each trench has its own ecosystems.
Apart from the exciting discovery of the new snailfish, the expedition’s landers videoed supergiant amphipods from a 5,000-meter depth, and brought up volcanic glass and rock samples. The team said those samples are remnants of some of the earliest volcanic eruptions of the Mariana area, and would shed fresh light on the geology of the trench system.
In 1960 Jacques Piccard and Don Walsh undertook the deepest dives into the Mariana Trench in crewed vehicles down to 35,814 feet. In 2012 film director James Cameron dove to about 35,756 feet. Cameron is the explorer-in-residence for National Geographic.
The activity within subduction zones like the Mariana Trench and other deep points takes place about 420 miles below the Earth’s surface, and thus remains largely a mystery. Even so, subsequent dives into the depths bring more information and insights corroborated by samples of rocks and sea creatures. The sailfish’s presence proves that there are more deep trench ecosystems yet unknown to man. Each expedition pushes the frontiers further and discovers new realms.
By Bina Joseph
Photo by tata_aka-T – Flickr License