Why do trenches form

Click for More Information and to Order. Volcanic arcs Volcanic arcs form above overriding plates in subduction zones. A volcanic arc is a belt of volcanoes that are fueled by the melting subducting plate. The Cascade Volcanoes are a volcanic arc that stretches miles southward from British Columbia to Northern California on the continental side of the Cascadia Subduction Zone.

The Aleutian Trench separates the two plates. Kids Fun Science Bookstore. School Books. Fun Science Books. Activity Books. Ocean trenches remain one of the most elusive and little-known marine habitats. Until the s, many oceanographer s thought that these trenches were unchanging environments nearly devoid of life. Even today, most research on ocean trenches has relied on seafloor samples and photographic expedition s.

That is slowly changing as explorers delve into the deep—literally. Two other unmanned expeditions have also explored the Challenger Deep. Engineering submersible s to explore ocean trenches is presents a huge set of unique challenges. Submersibles must be incredibly strong and resilient to contend with strong ocean current s, no visibility, and intense pressure of the Mariana Trench. Engineering a submersible to safely transport people, as well as delicate equipment , is even more challenging.

The sub that took Piccard and Walsh to the Challenger Deep, the remarkable Trieste , was an unusual vessel called a bathyscaphe. To combat deep-sea currents, the sub was designed to spin slowly as it descended. Lights on the sub were not incandescent or fluorescent bulbs, but arrays of tiny LED s that illuminate d an area of about 30 meters feet. To adapt to the pressure of the deep, the sub was shaped like a sphere —the walls of a square or cylinder -shaped vessel would need to be at least three times thicker to avoid being crushed.

Perhaps most startlingly, the Deepsea Challenger itself was designed to compress. Ocean Deep. Ocean trenches were not studied and explored until the 20th century. Today, the Challenger Deep is the deepest part of the Mariana trench, while the Horizon Deep is the deepest part of the Tonga trench.

Mount Everest could fit inside the Mariana Trench with more than 2 kilometers 1 mile to spare. Developed after the bathysphere. Also called a collision zone. Also called a food cycle. Also called the geosphere. Ring of Fire. Also called visual range. Media Credits The audio, illustrations, photos, and videos are credited beneath the media asset, except for promotional images, which generally link to another page that contains the media credit.

Media If a media asset is downloadable, a download button appears in the corner of the media viewer. Text Text on this page is printable and can be used according to our Terms of Service. Interactives Any interactives on this page can only be played while you are visiting our website. Related Resources. Plate Tectonics. View Collection. Puerto Rico Trench. View Map. Protecting the Mariana Trench. View Activity. Educational Resources in Your Inbox.

Trenches are formed by subduction, a geophysical process in which two or more of Earth's tectonic plates converge and the older, denser plate is pushed beneath the lighter plate and deep into the mantle, causing the seafloor and outermost crust the lithosphere to bend and form a steep, V-shaped depression.

Subduction also generates an upwelling of molten crust that forms mountain ridges and volcanic islands parallel to the trench. Examples of these volcanic "arcs" can be seen in the Japanese Archipelago, the Aleutian Islands, and many other locations around this area called the Pacific "Ring of Fire. Trenches are long, narrow and very deep and, while most are in the Pacific Ocean, can be found around the world. The deepest trench in the world, the Mariana Trench located near the Mariana Islands, is 1, miles long and averages just 43 miles wide.

It is home to the Challenger Deep, which, at 10, meters 35, feet , is the deepest part of the ocean. The Tonga, Kuril-Kamatcha, Philippine, and Kermadec Trenches all contain depths greater than 10, meters 33, feet. The great depth of ocean trenches creates an environment with water pressures more than 1, times greater than the surface, constant temperatures just above freezing, and no light to sustain photosynthesis. While this may not seem like conditions suitable to life, the combination of extremely high pressure, the gradual accumulation of food along trench axes, and the geographical isolation of hadal systems are believed to have created habitats with an extraordinarily high abundance of a few highly specialized organisms.

Many of the organisms living in trenches have evolved surprising ways to survive in these unique environments. Recent discoveries in the hadal zone have revealed organisms with proteins and biomolecules suited to resisting the crushing hydrostatic pressure and others able to harness energy from the chemicals that leak out of hydrocarbon seeps and mud volcanoes on the seafloor.

Other hadal species thrive on the organic material that that drifts down from the sea surface and is funneled to the axis of the V-shaped trenches.

Because of their extreme depth, trenches present unique logistical and engineering challenges for the researchers who want to study them. Trench exploration to date has been extremely limited only three humans have ever visited the seafloor below 6, meters and much of what is known about trenches and the things that live there has been derived from two sampling campaigns in the s the Danish G alathea and the Soviet Vitjaz Expeditions and from a handful of photographic expeditions and seafloor samples taken remotely from the deep with little knowledge of their precise location.

Despite their scarcity, these initial attempts at studying trenches have hinted at the existence of previously unknown processes, species, and ecosystems. Knowledge of ocean trenches is limited because of their depth and their remoteness, but scientists do know they play a significant role in our lives on land. Seafloor earthquakes generated in subduction zones were responsible for the Indian Ocean tsunami and for the Tohoku Earthquake and tsunami in Japan.

By studying ocean trenches, scientists can better understand the physical process of subduction and the causes of these devastating natural disasters. The study of trenches also gives researchers insight into the novel and diverse adaptations of deep-sea organisms to their surroundings that may hold the key to biological and biomedical advances. Studying the way that hadal organisms have adapted to life in their harsh surroundings could help advance understanding in many different areas of research, from diabetes treatments to improved laundry detergents.

Researchers have already discovered microbes inhabiting deep-sea hydrothermal vents that hold potential as new sources of antibiotics and anti-cancer drugs. The discovery presents opportunities for further research on the role of trenches both as a source through volcanism and other processes and a sink in the planetary carbon cycle that could influence the way scientists eventually come to understand and predict the impacts of human-generated greenhouse gases and global climate change.

Many scientists and even philosophers like Socrates felt that life could not exist at these depths. He asserted from his findings that life could not exist at depths of more than feet m. This notion was challenged in by naturalists Michael and George Ossian Sars.

They found a sea lily which is an animal in a Norwegian fjord at a depth of 10 feet m. The British decided to explore deep-sea life. Between and , the British HMS Challenger sailed over seventy-nine thousand miles on this endeavor. They found a fantastic variety of life and categorized four thousand seven hundred new marine species. Piccard claimed to see a large flatfish that was about twelve inches long. Scientists have been doubtful about this claim and postulate that what Piccard saw was actually a sea cucumber.

A new species of snailfish was detected at feet m was found in December This was a record-breaking find as no other living fish has been found deeper than this. Recently there have been many discoveries, and the conclusion is the deep-sea trenches are teaming with life. Gigantism seems to affect life in the hadal zone. All species seem much larger than their counterparts that exist at shallower ocean depths.

Oceanic trenches have no light, and it is utterly dark in these depths. Some animals have responded to the challenge by developing huge eyes to capture the faintest trace of light. An example of this is the Stout Blacksmelt fish. The vision of other animals has completely vanished, and they rely on vibrations and touch to move around and catch prey.

The tripod fish is an excellent example of this. Other animals have learned to make their own light, known as bioluminescence, as seen in the lanternfish. The lack of light does not allow for plant growth, and so food is limited. Animals in deep-sea trenches have adapted to eat scraps of dead organisms and detritus that filter down through the water. These scraps of organisms are known as marine snow.

Sometimes dead whales are heavy enough to sink into the ocean trenches, which provides a feast for the animals that occupy the trench depths. Normal body fat would solidify in these conditions. The animals have adapted by storing unsaturated fats, which remain liquid even in extreme temperatures.

The cells in deep-sea animals have been adapted to include a tiny organic molecule known as piezolytes. Piezolytes bind to the water and give the proteins space to expand and change shape as they function in the body.

Proteins in normal cells would not be able to operate at such extreme temperatures and pressures. Fish seem to live at a maximum-depths of 26 to 27 feet.

Beyond that, there are other life forms, such as crustaceans known as amphipods. The amphipods grow to giant sizes in the deep cold water. Most normal amphipods are approximately an inch to two inches long, but they grow to more than a foot long in the trenches.

As they look like giant shrimp, it gives an impression of an alien world down in the depths. Single-cell organisms, similar to amoeba, known as foraminifera, have been found in giant sizes in ocean trenches. Huge sea cucumbers were also discovered inhabiting deep areas. Most of the animals found at great ocean depths do not have standard bone structure or air-filled spaces — the enormous pressure would shatter them if they did.

Jellyfish and soft-bodied animals cope much better with the increased pressure. Dumbo octopuses have been found at 32 feet m in the Mariana Trench. They do not look like the octopuses found closer to the surface. They have very deep-set eyes, with tiny tentacles and two ear-type appendages. Ping-Pong Tree Sponges look like transparent ping pong balls attached to a stalk. The ping pong ball sponges trap any creature that comes near and slowly consume it.

These unusual creatures are found at the deepest levels in the trenches. Frilled sharks have six or seven gills most normal sharks have five gills and more closely resemble eels than sharks.