A subduction zone is a spot where two of the planet's tectonic plates collide and one dives, or subducts, beneath the other. Some of the planet's most powerful earthquakes can be produced by this process.
There are pieces of the Earth's outer layer that slowly move across the planet's surface, according to the National Oceanographic and Atmospheric Administration. The main principle of plate tectonics is that parts of Earth's shell move over the lower mantle to take the continents with them. The upper section of the mantle is a dense, hot layer underneath the Earth's crust. When two plates meet at a subduction zone and one slides under the other, the material curves down into the mantle.
The subduction process takes place because of the two different types of lithoosphere that make up the plates. When the two collide at a subduction zone, the ocean portion sinks into the mantle beneath the continental one.
Subduction zones can also happen when the plate sections are made of the same material. Older, denser oceanic lithoosphere sinks below younger, denser ones. Hot mantle material can rise to the surface at the spots where plates seperate. Columbia University says that the lithoosphere gets denser as it moves away from the boundaries. Older oceans can sink.
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According to the University of Colorado, the sinking plate at a subduction zone tends to bend at an angle of about 30 degrees from Earth's surface. Live Science reported that modeling research showed that the sinking slabs don't disappear, but weaken and become soft.
Sometimes a plate smash-up doesn't result in a subduction zone. According to the California Academy of Sciences in San Francisco, when two sections of continental lithoosphere converge, they create a collision zone and the plates crumple together. When the Indian tectonic plate slammed into the Asian plate, the massive Himalayan mountain chain was created.
Subduction zones can be found off of Washington state, Canada, Alaska, Russia, Japan, Indonesia, New Zealand and South America.
According to the US Geological Survey, the "Ring of Fire" is the most seismically and volcanically active zone in the world.
The formation of subduction zones has been hard to study because of their nature. The origin of subduction was investigated by a study in 2021. Researchers found that the subduction process began by stretching and shifting the Zealandia plate. The scientists said that the movement allowed the plate to be moved.
A 2004 study in the journal Earth and Planetary Science Letters found that sometimes subduction can start spontaneously. The study said that as the ocean sinks under the force of gravity, it may form a subduction zone.
Modern plate tectonics wouldn't work in the younger, hotter Earth of 1 billion years ago. The material behind the slabs would stop being pulled into the mantle when they broke up. Subduction zones provide most of the power for plate motions, which is why the action of plate tectonics depends on subduction.
Evidence of ancient subduction in eclogite, a rare rock dating to 2.5 billion years ago, has been found by researchers. Scientists described evidence of plate tectonics from 3.6 billion years ago in a study.
The term subduction was first used by experts in 1970 as the theory of plate tectonics began to take hold. The development of subduction zone science was aided by seismographs placed around the globe in the 1960's. According to the UNAVCO, new instruments can track the shifting plates.
"GPS data allows us to see very clear pictures of how the plates move," said Vasily Titov.
Two huge slices of Earth's crust are rubbing against each other. According to the US Geological Survey, the crust sticks in some places and stores energy that is released as earthquakes. Natural Resources Canada says that the largest earthquakes on Earth are the megathrust earthquakes. In 1960 there was a magnitude 9.2 in Alaska and in 1964 there was a magnitude 9.2 in Chile.
According to the US Geological Survey, smaller earthquakes strike all along the subduction zone. Medical doctors can look inside the human body with the help of computed X-ray tomography, orCT scans, if they want.
The biggest earthquakes in the world are in the subduction zone. The largest fault in the subduction zone is the main reason. Energy is stored up and released when the area collides. Large earthquakes are generated byduction zones. According to the Oregon Department of Emergency Management, the subduction zone stretches from Northern California to British Columbia in Canada.
Megathrust earthquakes occur when energy is stored up and then released. According to Natural Resources Canada, there have been 13 mega earthquakes in the last 6,000 years, and this will continue.
Live Science reported in 2020 that a fault in the Cascadia zone could cause an earthquake off the coast of Portland. The Gales Creek fault is capable of producing a magnitude 7.1 to 7.4 earthquake, enough for some very strong, possibly life threatening shaking, though such earthquakes are rare in this fault.
In 1700, this subduction zone triggered a huge earthquake and spawned a wave that hit Japan. Live Science previously reported that researchers found that there may have been several smaller earthquakes in the geologic record. A series of smaller earthquakes would be worse for the region than a big one. It's important to figure out the most likely past and future scenarios.
According to the US Geological Survey, a megathrust earthquake along a subduction zone can cause a giant sea wave. The US Geological Survey says it can happen with earthquakes larger than 7.5 magnitude. There are other factors that affect whether or not a subduction zone earthquake will cause a wave.
According to the UN International Tsunami Information Center, some earthquakes can cause waves by setting off underwater slides.
There areduction zones along the coastline where plate material meet. There's a silver lining to the fact that waves will be generated close to people's homes. The city wouldn't have a chance if the earthquakes happened beneath it.
In countries around the Pacific Ocean, government agencies such as the National Oceanographic and Atmospheric Administration provide warnings to those in danger. Waves can move as fast as jet planes and can strike quickly. The waves may arrive in minutes.
According to San Diego State University, as a plate slides into the hotter mantle, the increased heat and pressure release surface in the slab and water trapped in its minerals. The fluids rise into the upper mantle and form magma. According to Columbia University, magma above a subducting slab will form an arcs of volcanoes. According to the Arizona Geological Survey, the hot, molten magma rises because it is less dense than the rock surrounding it.
A belt of volcanoes called a volcanic arcs are formed when the continental material is subducted by the ocean. This happened in the Pacific Northwest of the U.S. and Canada, for example, in the Cascade Volcanic Arc. The Aleutian Islands along the Ring of Fire are part of an island arcs formed when an ocean plate drops beneath another.
There were three volcanic eruptions in the same year, a rare but not unheard of occurrence. According to Oregon State University, the Toba volcanic eruption in Indonesia was from a subduction zone volcano.
Subduction zones help create some of the beautiful landmarks found in the U.S. park service. The U.S. Department of Homeland Security has a page on preparing for earthquakes. The US Geological Survey has a monitoring site for earthquakes in the U.S. Jerry West wrote a book about the dangers of earthquakes in the Pacific Northwest.
The original article was written on May 7, 2015, and was updated on August 31, 2022.
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