Convergent Plate Boundaries—Subduction Zones
- Cascadia Subduction Zone. The Pacific Northwest is an exciting place to observe geologic processes in action. National...
- Ancient Subduction in the Sierra Nevada. A glance at a map of the western United States might suggest that the Sierra...
- Southern Alaska Subduction Zone. Five park sites in southern Alaska showcase...
Where can you find a divergent continental plate boundary?
Unlike convergent boundaries, divergence occurs between only oceanic or only continental plates, not one of each. The vast majority of divergent boundaries are found in the ocean, where they were not mapped or understood until the mid-to-late 20th century. In divergent zones, the plates are pulled, and not pushed, apart.
Where on Earth can you find a convergent boundary?
They are generally areas of orogeny or mountain building. The teeth along the convergent boundaries mark the upper side, which is overriding the other side. The convergent boundaries correspond to subduction zones where an oceanic plate is involved. Where two continental plates collide, neither is dense enough to subduct below the other.
Where on Earth can you find a plate boundary?
You can find transform boundaries on the north side of Africa, the west side of North America, the north of South America, the southwest of south America west, the east side of India, and the south east and east of South America. How would you describe the motion of plates in a collision zone?
Where are the major tectonic plates located?
Main tectonic plates The North American plate is located around the North American continent. The main known tectonic plates are fifteen: African plate. Located around the African continent. Antarctic plate. Located around the Antarctic continent and the South Pole. Arabic plate. Located around the Middle East. A plate of Coconuts.
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What are the 3 convergent plate boundaries?
Three types of convergent boundaries are recognized: continent‐continent, ocean‐continent, and ocean‐ocean.
What are convergent boundaries and where do they occur?
Convergent (Colliding): This occurs when plates move towards each other and collide. When a continental plate meets an oceanic plate, the thinner, denser, and more flexible oceanic plate sinks beneath the thicker, more rigid continental plate.
Which is the best example of a convergent plate boundary?
The Pacific Ring of Fire is an example of a convergent plate boundary. At convergent plate boundaries, oceanic crust is often forced down into the mantle where it begins to melt. Magma rises into and through the other plate, solidifying into granite, the rock that makes up the continents.
What are examples of convergent boundaries?
Three examples of convergent plate boundaries are: Himalaya Mountains in Central Asia. Western Andes Mountains in South America. Northern Cascade Mountains in the Pacific Northwest America.
Where do divergent boundaries occur?
Divergent boundaries. Divergent boundaries occur along spreading centers where plates are moving apart and new crust is created by magma pushing up from the mantle.
Where do continental continental convergence occur?
Big mountains! The best place to see two continental plates converging is in the Himalaya Mountains. These mountains are the highest above sea level on Earth. They are very popular with mountain climbers.
Where do transform boundaries occur?
Transform boundaries are places where plates slide sideways past each other. At transform boundaries lithosphere is neither created nor destroyed. Many transform boundaries are found on the sea floor, where they connect segments of diverging mid-ocean ridges. California's San Andreas fault is a transform boundary.
What does a convergent boundary form?
Convergent boundaries can form mountains, volcanos, or subduction zones that form large trenches. When two plates collide, the crusts can push together to form mountain ranges. This is how the Himalayan mountains were formed. Convergent boundaries between oceanic and continental boundaries feature a subduction zone.
How does a convergent boundary occur?
When a convergent boundary occurs between two oceanic plates, one of those plates will subduct beneath the other. Normally the older plate will subduct because of its higher density. The subducting plate is heated as it is forced deeper into the mantle, and at a depth of about 100 miles (150 km) the plate begins to melt. Magma chambers are produced as a result of this melting, and the magma is lower in density than the surrounding rock material. It begins ascending by melting and fracturing its way through the overlying rock material. Magma chambers that reach the surface break through to form a volcanic eruption cone. In the early stages of this type of boundary, the cones will be deep beneath the ocean surface but later grow to be higher than sea level. This produces an island chain. With continued development the islands grow larger, merge, and an elongate landmass is created.
Which plate boundary is subducting beneath the South American plate?
The Andes Mountain Range of western South America is another example of a convergent boundary between an oceanic and continental plate. Here the Nazca Plate is subducting beneath the South American plate. Visit the Interactive Plate Boundary Map to explore satellite images of convergent boundaries between oceanic and continental plates.
What is the effect of partial melting on the oceanic plate?
This partial melting produces magma chambers above the subducting oceanic plate. These magma chambers are less dense than the surrounding mantle materials and are buoyant. The buoyant magma chambers begin a slow ascent through the overlying materials, melting and fracturing their way upwards.
How deep does the oceanic plate go?
As the oceanic plate descends, it is forced into higher temperature environments. At a depth of about 100 miles (160 km), materials in the subducting plate begin to approach their melting temperatures and a process of partial melting begins. ADVERTISEMENT.
What happens when continental plates collide?
When continental and oceanic plates collide, the thinner and more dense oceanic plate is overridden by the thicker and less dense continental plate. The oceanic plate is forced down into the mantle in a process known as "subduction.". As the oceanic plate descends, it is forced into higher temperature environments.
What are the effects of plate boundary?
Effects that are found at this type of plate boundary include: a zone of progressively deeper earthquakes; an oceanic trench; a chain of volcanic islands; the destruction of oceanic lithosphere.
What happens if a magma chamber rises to the surface without solidifying?
If a magma chamber rises to the surface without solidifying, the magma will break through in the form of a volcanic eruption. The Washington-Oregon coastline of the United States is an example of this type of convergent plate boundary.
What is the process of convergent plate boundary?
Where tectonic plates converge, a plate capped by thin oceanic crust descends (subducts) beneath a plate with much thicker continental crust. The landscapes of many National Park Service sites show convergent plate boundary processes that result in a variety of mountain ranges and complex geological structures characteristic of subduction zones, accreted terranes and collisional mountain ranges.
Where do tectonic plates converge?
Where tectonic plates converge, the one with thin oceanic crust subducts beneath the one capped by thick continental crust. A subduction zone consists of material scraped off the ocean floor near the coast (accretionary wedge) and a chain of volcanoes farther inland (volcanic arc).
How do continents grow outward?
Continents grow outward as volcanic islands and continental fragments enter a subduction zone and attach to the edge of the continent. Examples of such accreted terranes are found in NPS sites in southern Alaska and northern Washington State. Sometimes plate convergence closes an entire ocean. The crusts of the continents are too thick and buoyant to subduct, forming a collisional mountain range, such as the Appalachian/Ouachita/Marathon chain in the eastern United States and the Brooks Range in northern Alaska.
What is the name of the region where the continental crust lifts up a broad region known as a collisional?
Continents collide where subduction completely closes an ocean. The buoyant continental crust lifts up a broad region known as a collisional mountain range.
Where are the two mountain ranges formed during plate convergence?
The Cascadia Subduction Zone and Southern Alaska Subduction Zone reveal two mountain ranges formed during plate convergence: an accretionary wedge near the coast and a volcanic arc farther inland. Rocks in California’s Sierra Nevada are cooled magma chambers that fed volcanoes of an ancient subduction zone. Examples of accreted terranes are found in southeast Alaska and northern Washington state. The Appalachian, Ouachita, and Marathon mountains comprise a collisional mountain range formed 500 to 300 million years ago, whereas the Brooks Range is the result of a more recent continental collision.
Where are accreted terranes found?
Examples of accreted terranes are found in southeast Alaska and northern Washington state. The Appalachian, Ouachita, and Marathon mountains comprise a collisional mountain range formed 500 to 300 million years ago, whereas the Brooks Range is the result of a more recent continental collision.
What is the process of convergent plate boundary?
Where tectonic plates converge, a plate capped by thin oceanic crust descends (subducts) beneath a plate with much thicker continental crust. The landscapes of many National Park Service sites show convergent plate boundary processes that result in a variety of mountain ranges and complex geological structures characteristic of subduction zones, accreted terranes and collisional mountain ranges.
Where do tectonic plates converge?
Where tectonic plates converge, the one with thin oceanic crust subducts beneath the one capped by thick continental crust. A subduction zone consists of material scraped off the ocean floor near the coast (accretionary wedge) and a chain of volcanoes farther inland (volcanic arc).
What is the name of the region where the continental crust lifts up a broad region known as a collisional?
Continents collide where subduction completely closes an ocean. The buoyant continental crust lifts up a broad region known as a collisional mountain range.
Where are the two mountain ranges formed during plate convergence?
The Cascadia Subduction Zone and Southern Alaska Subduction Zone reveal two mountain ranges formed during plate convergence: an accretionary wedge near the coast and a volcanic arc farther inland. Rocks in California’s Sierra Nevada are cooled magma chambers that fed volcanoes of an ancient subduction zone. Examples of accreted terranes are found in southeast Alaska and northern Washington state. The Appalachian, Ouachita, and Marathon mountains comprise a collisional mountain range formed 500 to 300 million years ago, whereas the Brooks Range is the result of a more recent continental collision.
How do continents grow outward?
Continents grow outward as volcanic islands and continental fragments enter a subduction zone and attach to the edge of the continent. Examples of such accreted terranes are found in NPS sites in southern Alaska and northern Washington State. Sometimes plate convergence closes an entire ocean. The crusts of the continents are too thick and buoyant to subduct, forming a collisional mountain range, such as the Appalachian/Ouachita/Marathon chain in the eastern United States and the Brooks Range in northern Alaska.
What happens when a continental plate converges with another plate?
In some instances, initial convergence with another plate will destroy oceanic lithosphere, leading to convergence of two continental plates. Neither continental plate will subduct. It is likely that the plate may break along the boundary of continental and oceanic crust.
What is the region of active deformation between colliding tectonic plates?
Region of active deformation between colliding tectonic plates. Simplified diagram of a convergent boundary. A convergent boundary (also known as a destructive boundary) is an area on Earth where two or more lithospheric plates collide. One plate eventually slides beneath the other, a process known as subduction.
How do accretionary wedges form?
An accretionary wedge forms on the continental crust as deep-sea sediments and oceanic crust are scraped from the oceanic plate. Volcanic arcs form on continental lithosphere as the result of partial melting due to dehydration of the hydrous minerals of the subducting slab.
What is subduction zone?
Subduction zones are areas where one lithospheric plate slides beneath another at a convergent boundary due to lithospheric density differences. These plates dip at an average of 45° but can vary. Subduction zones are often marked by an abundance of earthquakes, the result of internal deformation of the plate, convergence with the opposing plate, ...
How does plate tectonics work?
Plate tectonics is driven by convection cells in the mantle. Convection cells are the result of heat generated by radioactive decay of elements in the mantle escaping to the surface and the return of cool materials from the surface to the mantle. These convection cells bring hot mantle material to the surface along spreading centers creating new crust. As this new crust is pushed away from the spreading center by the formation of newer crust, it cools, thins, and becomes denser. Subduction begins when this dense crust converges with less dense crust. The force of gravity helps drive the subducting slab into the mantle. As the relatively cool subducting slab sinks deeper into the mantle, it is heated, causing hydrous minerals to break down. This releases water into the hotter asthenosphere, which leads to partial melting of asthenosphere and volcanism. Both dehydration and partial melting occurs along the 1,000 °C (1,830 °F) isotherm, generally at depths of 65 to 130 km (40 to 81 mi).
What happens when a subducting slab sinks deeper into the mantle?
As the relatively cool subducting slab sinks deeper into the mantle, it is heated, causing hydrous minerals to break down. This releases water into the hotter asthenosphere, which leads to partial melting of asthenosphere and volcanism.
What happens when two oceanic plates collide?
In collisions between two oceanic plates, the cooler, denser oceanic lithosphere sinks beneath the warmer, less dense oceanic lithosphere. As the slab sinks deeper into the mantle, it releases water from dehydration of hydrous minerals in the oceanic crust.
What Happens At A Convergent Boundary?
Some or all of these activities happen at the convergent boundaries: subduction of the denser plate underneath the less dense one , melting of parts of the subducted plates, plate collision, faulting and folding, crustal deformation, magma generation, volcanic eruptions, and earthquakes.
When a continental and an oceanic plate collide at the convergent boundary of the two plates, what?
Continental-Oceanic. When a continental and an oceanic plate collide at the convergent boundary of the two plates, subduction zones often develop. The thinner and denser oceanic plate usually subducts below the thicker and less dense continental plate. Deep oceanic trenches are produced in the process and the subduction activity might lead ...
What happens to the tectonic plates at the subduction zone?
At the subduction zone of a convergent boundary, the denser tectonic plate slides underneath the relatively less dense plate. As the plate slides to greater depths of about 100 km below the surface of the Earth, it comes into contact with the relatively hotter environment of the mantle. As the fluids are released from the subducting plate into the hot mantle below, the process of partial melting of the parts of the subducted plate and the sediments carried by it begins to take place. Thus, a viscous and hot liquid called magma is generated which then moves up through the vent between the two sliding tectonic plates.
What happens when two plates collide?
Since two continental plates are colliding, subduction becomes questionable as the difference in density between the plates is usually quite low. Instead, subduction might happen to some extent if the heavier lithosphere below the crust might break free from it due to the forces of friction and pressure created at the convergent boundary. Such types of convergent boundaries are also subjected to extensive faulting and folding of the rocks within the two plates that are colliding with each other.
What is the name of the mountain range formed by a convergent plate boundary?
Fold mountain ranges form at convergent plate boundaries. When tectonic movements cause two tectonic plates to approach each other at the convergent plate boundary, deposits of sedimentary and metamorphic rocks at such boundaries often crumple and fold to form mountains called fold mountains. The presence of mechanically vulnerable layers like a layer of salt in such deposits speeds up the process of folding.
How were fold mountains formed?
These mountains were formed as a result of the collision between the Eurasian Plate and the Indo-Australian Plate at the convergent boundary. The Andaman and Nicobar Islands located in the Indian Ocean and part of the territory of India were also formed in a similar manner.
Where are volcanoes formed?
Volcanoes are formed at three locations on the crust of the Earth: at convergent boundaries, divergent boundaries, and hot spots. When two tectonic plates approach each other, ...
Which plate boundary formed between the Pacific and Pacific plates?
As the mid-ocean ridge separating the Farallon and Pacific Plates entered the subduction zone, the Farallon Plate separated into the Juan de Fuca and Cocos Plates. A transform plate boundary developed where the Pacific Plate was in contact with the North American Plate and the volcanism ceased in central California.
What is the wedge formed between the converging plates?
An accretionary wedge forms between the converging plates as material is scraped off the subducting plate.
What are the sites of subduction?
The Cascadia Subduction Zone and Southern Alaska are the sites of ongoing subduction as the Pacific and Juan de Fuca plates slide beneath the North American Plate. Some parks in the Sierra Nevada Mountains reveal igneous magma chamber rocks that represent the eroded remnants of an ancient subduction zone, when volcanoes similar to those found in the modern Cascade Mountains extended southward all the way through California.
What is the result of the subduction of the Juan de Fuca Plate?
Subduction of the Juan de Fuca Plate results in the formation of the Coastal Ranges and Cascade Volcanoes, as well as a variety of earthquakes, in the Pacific Northwest. Olympic and Mt. Rainier national parks showcase the contrasting landscapes of the two parallel mountain ranges.
What type of crust forms when a plate with thinner (less buoyant) oceanic crust descends beneath a?
Subduction zones form where a plate with thinner (less-buoyant) oceanic crust descends beneath a plate with thicker (more-buoyant) continental crust. Two parallel mountain ranges commonly develop above such a subduction zone – a coastal range consisting of sedimentary strata and hard rock lifted out of the sea ( accretionary wedge ), and a volcanic range farther inland ( volcanic arc ). Ancient magma chamber rocks can be exposed if subduction stops and the volcanoes erode away.
What are the two mountain ranges in the Cascadia subduction zone?
Parks in the Cascadia Subduction Zone dramatically display the two distinct mountain ranges – the Coast Range just above where the Juan de Fuca Plate begins to subduct, and the volcanic Cascade Range farther inland, where the top of the plate is deeper.
How far is the Juan de Fuca Plate?
Visitors to Olympic National Park, Oregon Caves National Monument, or Redwood National and State Parks can look down and imagine the top of the Juan de Fuca Plate about 10 miles (16 kilometers) beneath their feet.
What are the three types of plate boundaries?
Plate Boundaries: Divergent, Convergent, and Transform. YouTube. 0. Movement in narrow zones along plate boundaries causes most earthquakes. Most seismic activity occurs at three types of plate boundaries—divergent, convergent, and transform. As the plates move past each other, they sometimes get caught and pressure builds up.
What is the term for the process of a continental plate colliding with an oceanic plate?
Convergent (Colliding): This occurs when plates move towards each other and collide. When a continental plate meets an oceanic plate, the thinner, denser, and more flexible oceanic plate sinks beneath the thicker, more rigid continental plate. This is called subduction. Subduction causes deep ocean trenches to form, such as the one along the west coast of South America. The rocks pulled down under the continent begin to melt. Sometimes the molten rock rises to the surface, through the continent, forming a line of volcanoes. About 80% of earthquakes occur where plates are pushed together, called convergent boundaries.
What is the term for the movement of two plates away from each other?
Divergent (Spreading) :This is where two plates move away from each other. Molten rock from the mantle erupts along the opening, forming new crust. The earthquakes that occur along these zones, called spreading centers, are relatively small. The Great Rift Valley in Africa, the Red Sea and the Gulf of Aden all formed as a result of divergent plate motion.
What happens when the plates move past each other?
As the plates move past each other, they sometimes get caught and pressure builds up. When the plates finally give and slip due to the increased pressure, energy is released as seismic waves, causing the ground to shake. This is an earthquake. Some of the plates have ocean water above them.
What happens when two tectonic plates slide past each other?
When two tectonic plates slide past each other, the place where they meet is a transform or lateral fault.
What are some examples of divergent plate boundaries?
The Mid-Atlantic Ridge and Pacific Ring of Fire are two examples of divergent plate boundaries. When two plates come together, it is known as a convergent boundary.
Where does the transform plate boundary occur?
One of the most famous transform plate boundaries occurs at the San Andreas fault zone, which extends underwater. Natural or human-made structures that cross a transform boundary are offset—split into pieces and carried in opposite directions.
What type of plate boundary is a chain of volcanoes?
A chain of volcanoes often forms parallel to convergent plate boundaries and powerful earthquakes are common along these boundaries. At convergent plate boundaries, oceanic crust is often forced down into the mantle where it begins to melt.
What is divergent boundary?
A divergent boundary occurs when two tectonic plates move away from each other. Along these boundaries, earthquakes are common and magma (molten rock) rises from the Earth’s mantle to the surface, solidifying to create new oceanic crust.
What are the three types of plate boundaries?
This image shows the three main types of plate boundaries: divergent, convergent, and transform. Image courtesy of the U.S. Geological Survey. Download image (jpg, 76 KB).
What happens when two plates slide past each other?
Magma rises into and through the other plate, solidifying into granite, the rock that makes up the continents. Thus, at convergent boundaries, continental crust is created and oceanic crust is destroyed. Two plates sliding past each other forms a transform plate boundary.
Overview
Subduction zones
- The Washington-Oregon coastline of the United States is an example of this type of convergent plate boundary. Here the Juan de Fuca oceanic plate is subducting beneath the westward-moving North American continental plate. The Cascade Mountain Range is a line of volcanoes above the melting oceanic plate. The Andes Mountain Range of western South Ame...
Oceanic – oceanic convergence
Continental – oceanic convergence
Continental – continental convergence
A convergent boundary (also known as a destructive boundary) is an area on Earth where two or more lithospheric plates collide. One plate eventually slides beneath the other, a process known as subduction. The subduction zone can be defined by a plane where many earthquakes occur, called the Wadati–Benioff zone. These collisions happen on scales of millions to tens of millions of year…
Volcanism and volcanic arcs
Subduction zones are areas where one lithospheric plate slides beneath another at a convergent boundary due to lithospheric density differences. These plates dip at an average of 45° but can vary. Subduction zones are often marked by an abundance of earthquakes, the result of internal deformation of the plate, convergence with the opposing plate, and bending at the oceanic trench. Earthquakes have been detected to a depth of 670 km (416 mi). The relatively cold and dense su…
Back-arc basins
In collisions between two oceanic plates, the cooler, denser oceanic lithosphere sinks beneath the warmer, less dense oceanic lithosphere. As the slab sinks deeper into the mantle, it releases water from dehydration of hydrous minerals in the oceanic crust. This water reduces the melting temperature of rocks in the asthenosphere and causes partial melting. Partial melt will travel up through the asthenosphere, eventually, reach the surface, and form volcanic island arcs.
Oceanic trenches
When oceanic lithosphere and continental lithosphere collide, the dense oceanic lithosphere subducts beneath the less dense continental lithosphere. An accretionary wedge forms on the continental crust as deep-sea sediments and oceanic crust are scraped from the oceanic plate. Volcanic arcs form on continental lithosphere as the result of partial melting due to dehydration of the hydrous minerals of the subducting slab.