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Deep ocean trenches

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Deep-sea trenches are long, deep ocean depressions that form at subduction zones where one tectonic plate slides under another. The deepest is the Mariana Trench near Guam, with the Challenger Deep reaching 10,994 meters below sea level. Trenches form as the leading edge of a heavy plate bends downward due to subduction under a lighter plate. This process also creates volcanic island arcs and causes powerful earthquakes. Life in trenches survives under immense pressure, with microbes like foraminifera the only organisms collected so far from the deepest parts.

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By Connor
 Deep-sea trenches generally lie seaward and parallel to arcs or mountain ranges of the continental margins.  They are closely associated with and found in subduction zones— that is, locations where a lithospheric plate bearing oceanic crust slides down into the upper mantle under the force of gravity.
 Both types of subduction zones are associated with large earthquakes that originate at a depth of as much as 700 km (435 miles).  The deep earthquakes below subduction zones occur in a plane that dips 30° or more under the overriding plate.  Typical trench depths are 8 to 10 km (5 to 6 miles). The longest trench is the Peru-Chile Trench, which extends some 5,900 km (about 3,700 miles) along the west coast of South America.
 Ocean trenches are the deepest parts of the ocean. They are also called submarine valleys.  An ocean trench is a long, deep depression in the ocean floor, similar to deep chasms on the Earth’s dry land.  Some trenches are near continental shelves. Others are found near chains of volcanic islands, often called volcanic arcs.  Some volcanic arcs include the Aleutians, and the island nations of Japan and the Philippines
 Trenches are formed as a result of plate tectonics, or the movement of the Earth’s crust.  Tectonic plates slip underneath each other in a process known as subduction.  When the leading edge of a heavy plate meets the edge of a lighter plate, the heavier plate bends downward.  This place where the heavier plate melts (subducts) beneath the lighter one is called the subduction zone.
 Ocean trenches can be formed by subduction between continental crust and oceanic crust. Continental crust is always lighter.  The long series of Peru-Chile Trenches off the west coast of South America is formed by the oceanic crust of the Nazca plate subducting beneath the continental crust of the South American plate.  Ocean trenches can also be formed when two plates carrying oceanic crust meet. These are more rare.
 The Mariana Trench, in the South Pacific Ocean, is formed as the massive Pacific plate subducts beneath the Philippine plate.  The deepest place on Earth is called the Challenger Deep. It is found in the Mariana Trench in the Pacific Ocean, near the island of Guam.  The Challenger Deep is 10,994 meters (36,070 feet) below the ocean’s surface.  For comparison, Mount Everest, the world’s tallest mountain, is 8,850 meters (29,035 feet) above sea level. Mount Everest could fit inside the Mariana Trench with more than 2 kilometers (1 mile) to spare
 In June 2009, scientists sent an unmanned deep-sea robot, the Nereus, to explore the Mariana Trench and Challenger Deep.  The vehicle had to be designed to withstand extreme pressure of 15,000 pounds per square inch— more than 1,000 times the pressure felt at sea level.  Scientists want to learn more about the subduction process that created the trench.
 The deepest part of the Atlantic Ocean is the Puerto Rico Trench.  It is just over 8,600 meters (28,232 feet) deep and is about 280 kilometers (175 miles) long.  The Puerto Rico Trench was formed by the North Atlantic plate sliding beneath the Caribbean plate.
 Animals that live in ocean trenches have to survive a habitat of extreme pressure.  Most organisms collected from the Challenger Deep have been microscopic. The organisms, or foraminifera, are similar to algae or slime-molds.  Scientists believe the foraminifera they found at the bottom of the Challenger Deep are similar to Earth’s earliest life forms.
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Deep ocean trenches

  • 2.  Deep-sea trenches generally lie seaward and parallel to arcs or mountain ranges of the continental margins.  They are closely associated with and found in subduction zones— that is, locations where a lithospheric plate bearing oceanic crust slides down into the upper mantle under the force of gravity.
  • 3.  Both types of subduction zones are associated with large earthquakes that originate at a depth of as much as 700 km (435 miles).  The deep earthquakes below subduction zones occur in a plane that dips 30° or more under the overriding plate.  Typical trench depths are 8 to 10 km (5 to 6 miles). The longest trench is the Peru-Chile Trench, which extends some 5,900 km (about 3,700 miles) along the west coast of South America.
  • 4.  Ocean trenches are the deepest parts of the ocean. They are also called submarine valleys.  An ocean trench is a long, deep depression in the ocean floor, similar to deep chasms on the Earth’s dry land.  Some trenches are near continental shelves. Others are found near chains of volcanic islands, often called volcanic arcs.  Some volcanic arcs include the Aleutians, and the island nations of Japan and the Philippines
  • 5.  Trenches are formed as a result of plate tectonics, or the movement of the Earth’s crust.  Tectonic plates slip underneath each other in a process known as subduction.  When the leading edge of a heavy plate meets the edge of a lighter plate, the heavier plate bends downward.  This place where the heavier plate melts (subducts) beneath the lighter one is called the subduction zone.
  • 6.  Ocean trenches can be formed by subduction between continental crust and oceanic crust. Continental crust is always lighter.  The long series of Peru-Chile Trenches off the west coast of South America is formed by the oceanic crust of the Nazca plate subducting beneath the continental crust of the South American plate.  Ocean trenches can also be formed when two plates carrying oceanic crust meet. These are more rare.
  • 7.  The Mariana Trench, in the South Pacific Ocean, is formed as the massive Pacific plate subducts beneath the Philippine plate.  The deepest place on Earth is called the Challenger Deep. It is found in the Mariana Trench in the Pacific Ocean, near the island of Guam.  The Challenger Deep is 10,994 meters (36,070 feet) below the ocean’s surface.  For comparison, Mount Everest, the world’s tallest mountain, is 8,850 meters (29,035 feet) above sea level. Mount Everest could fit inside the Mariana Trench with more than 2 kilometers (1 mile) to spare
  • 8.  In June 2009, scientists sent an unmanned deep-sea robot, the Nereus, to explore the Mariana Trench and Challenger Deep.  The vehicle had to be designed to withstand extreme pressure of 15,000 pounds per square inch— more than 1,000 times the pressure felt at sea level.  Scientists want to learn more about the subduction process that created the trench.
  • 9.  The deepest part of the Atlantic Ocean is the Puerto Rico Trench.  It is just over 8,600 meters (28,232 feet) deep and is about 280 kilometers (175 miles) long.  The Puerto Rico Trench was formed by the North Atlantic plate sliding beneath the Caribbean plate.
  • 10.  Animals that live in ocean trenches have to survive a habitat of extreme pressure.  Most organisms collected from the Challenger Deep have been microscopic. The organisms, or foraminifera, are similar to algae or slime-molds.  Scientists believe the foraminifera they found at the bottom of the Challenger Deep are similar to Earth’s earliest life forms.