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We also offer digital copies of our proposals and reviews for download. Video lecture on divergent, transform, and convergent types of plate boundaries. Recorded during a teacher workshop on earthquakes and tectonics. Speaker is Dr.Types of Plate Boundaries
Robert Butler, University of Portland Oregon. Conceptual model of the relative thicknesses of the Lithosphere relative to the diameter of the Earth uses a hard-boiled egg to gain understanding about the scale of the lithospheric plates.
New oceanic crust is created at this boundary when basalt magma, formed in the mantle, rises into fractures in the crust and solidifies.
Spreading ridges are high elevation because the young oceanic plate at the ridge crest is hot and less dense than the older, colder and more dense plate on the flanks of the ridge. The subduction zone iswhere two tectonic lithospheric plates come together, one subducting diving beneath the other.
The plates are locked together and periodically overcome the friction causing the leading edge of the overlying plate to surge back, lifting a wall of water producting a tsunami.
A transform fault is a type of strike-slip fault wherein the relative horizontal slip is accommodating the movement between two ocean ridges or other tectonic boundaries. They are connected on both ends to other faults. In a normal fault, the block above the fault moves down relative to the block below the fault. This fault motion is caused by tensional forces and results in extension.What are the four types of plate boundaries? There are three main types of plate boundaries:.
Convergent boundaries: where two plates are colliding. Subduction zones occur when one or both of the tectonic plates are composed of oceanic crust. Divergent boundaries — where two plates are moving apart. Transform boundaries — where plates slide passed each other. See Full Answer. What is the 3 types of plate boundaries? There are three kinds of plate tectonic boundaries : divergent, convergent, and transform plate boundaries. This image shows the three main types of plate boundaries : divergent, convergent, and transform.
Image courtesy of the U. Geological Survey. Plates move towards one another at convergent boundaries; one plate is forced below another in a process called subduction.
Earthquakes and composite volcanoes are common at this type of boundary. Plates move past on another at transform boundaries.
There are three types of convergent boundaries each with its own consequences. Oceanic-Continental Convergence. The first type of convergent boundary is Oceanic-Continetal Convergence. Oceanic-Oceanic Convergence. The next type is Oceanic-Oceanic Convergence. Continental-Continental Convergence. What is a plate boundary in geography?
A constructive plate boundarysometimes called a divergent plate marginoccurs when plates move apart. Volcanoes are formed as magma wells up to fill the gap, and eventually new crust is formed. An example of a constructive plate boundary is the mid-Atlantic Ridge. An earthquake is the shaking and vibration of the Earth's crust due to movement of the Earth's plates plate tectonics. Earthquakes can happen along any type of plate boundary.
Earthquakes occur when tension is released from inside the crust. Plates at our planet's surface move because of the intense heat in the Earth's core that causes molten rock in the mantle layer to move.Scientists now have a fairly good understanding of how the plates move and how such movements relate to earthquake activity. Most movement occurs along narrow zones between plates where the results of plate-tectonic forces are most evident. Divergent boundaries occur along spreading centers where plates are moving apart and new crust is created by magma pushing up from the mantle.
Picture two giant conveyor belts, facing each other but slowly moving in opposite directions as they transport newly formed oceanic crust away from the ridge crest. Perhaps the best known of the divergent boundaries is the Mid-Atlantic Ridge.
This submerged mountain range, which extends from the Arctic Ocean to beyond the southern tip of Africa, is but one segment of the global mid-ocean ridge system that encircles the Earth. The rate of spreading along the Mid-Atlantic Ridge averages about 2. This rate may seem slow by human standards, but because this process has been going on for millions of years, it has resulted in plate movement of thousands of kilometers.
Seafloor spreading over the past to million years has caused the Atlantic Ocean to grow from a tiny inlet of water between the continents of Europe, Africa, and the Americas into the vast ocean that exists today. The volcanic country of Iceland, which straddles the Mid-Atlantic Ridge, offers scientists a natural laboratory for studying on land the processes also occurring along the submerged parts of a spreading ridge. Iceland is splitting along the spreading center between the North American and Eurasian Plates, as North America moves westward relative to Eurasia.
The map also shows Reykjavik, the capital of Iceland, the Thingvellir area, and the locations of some of Iceland's active volcanoes red trianglesincluding Krafla. The consequences of plate movement are easy to see around Krafla Volcano, in the northeastern part of Iceland. Here, existing ground cracks have widened and new ones appear every few months.
From tonumerous episodes of rifting surface cracking took place along the Krafla fissure zone. Some of these rifting events were accompanied by volcanic activity; the ground would gradually rise m before abruptly dropping, signalling an impending eruption. Between andthe displacements caused by rifting totalled about 7 m. When the continental crust stretches beyond its limits, tension cracks begin to appear on the Earth's surface.
Magma rises and squeezes through the widening cracks, sometimes to erupt and form volcanoes. The rising magma, whether or not it erupts, puts more pressure on the crust to produce additional fractures and, ultimately, the rift zone.Plate boundaries are the edges where two plates meet. Most geologic activities, including volcanoes, earthquakesand mountain building, take place at plate boundaries. There are four types of plate boundaries: Divergent boundaries — where new crust is generated as the plates pull away from each other.
Convergent boundaries — where crust is destroyed as one plate dives under another. Occurs when two tectonic plates move away from each other. Along these boundaries, lava spews from long fissures and geysers spurt superheated water.
Frequent earthquakes strike along the rift. Beneath the rift, magma—molten rock—rises from the mantle. It oozes up into the gap and hardens into solid rock, forming new crust on the torn edges of the plates.
Magma from the mantle solidifies into basalt, a dark, dense rock that underlies the ocean floor. Thus at divergent boundaries, oceanic crust, made of basalt, is created. When two plates come together, The impact of the two colliding plates buckles the edge of one or both plates up into a rugged mountain range, and sometimes bends the other down into a deep seafloor trench. A chain of volcanoes often forms parallel to the boundary, to the mountain range, and to the trench.
Powerful earthquakes shake a wide area on both sides of the boundary. If one of the colliding plates is topped with oceanic crust, it is forced down into the mantle where it begins to melt. Magma rises into and through the other plate, solidifying into new crust. Magma formed from melting plates solidifies into granite, a light colored, low-density rock that makes up the continents. Thus at convergent boundaries, continental crust, made of granite, is created, and oceanic crust is destroyed.
Two plates sliding past each other, Natural or human-made structures that cross a transform boundary are offset—split into pieces and carried in opposite directions. Rocks that line the boundary are pulverized as the plates grind along, creating a linear fault valley or undersea canyon.
As the plates alternately jam and jump against each other, earthquakes rattle through a wide boundary zone. In contrast to convergent and divergent boundaries, no magma is formed.There are major plates and many minor plates. Varying between 0 to mm per year, the movement of a plate is driven by convection in the underlying hot and viscous mantle.
Earthquakes, volcanic activity, mountain-building, and oceanic trench formation occur along plate boundaries in zones that may be anything from a few kilometres to a few hundred kilometres wide. To watch a simulated fly-by along New Zealand's plate boundary check out this video. Subduction zones occur when one or both of the tectonic plates are composed of oceanic crust.
Four Types of Boundaries Between Tectonic Plates
The denser plate is subducted underneath the less dense plate. The plate being forced under is eventually melted and destroyed. Where oceanic crust meets ocean crust Island arcs and oceanic trenches occur when both of the plates are made of oceanic crust. Zones of active seafloor spreading can also occur behind the island arc, known as back-arc basins.
These are often associated with submarine volcanoes. Where oceanic crust meets continental crust The denser oceanic plate is subducted, often forming a mountain range on the continent. The Andes is an example of this type of collision. Where continental crust meets continental crust Both continental crusts are too light to subduct so a continent-continent collision occurs, creating especially large mountain ranges.
The most spectacular example of this is the Himalayas. The space created can also fill with new crustal material sourced from molten magma that forms below. Divergent boundaries can form within continents but will eventually open up and become ocean basins. On land Divergent boundaries within continents initially produce rifts, which produce rift valleys. Under the sea The most active divergent plate boundaries are between oceanic plates and are often called mid-oceanic ridges.
Stuck Plate Boundary. Slow Slip Events. New Zealands Largest Fault. Earthquakes and Faults. New Zealand Earthquakes. Major Faults in New Zealand.
Tectonic Plates and Plate Boundaries
Monitoring Earthquakes.This image shows the three main types of plate boundaries: divergent, convergent, and transform. Image courtesy of the U. Geological Survey. Download image jpg, 76 KB. A divergent boundary occurs when two tectonic plates move away from each other. When two plates come together, it is known as a convergent boundary. The impact of the colliding plates can cause the edges of one or both plates to buckle up into a mountain ranges or one of the plates may bend down into a deep seafloor trench.
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.
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.
Natural or human-made structures that cross a transform boundary are offset—split into pieces and carried in opposite directions. Rocks that line the boundary are pulverized as the plates grind along, creating a linear fault valley or undersea canyon. Earthquakes are common along these faults. In contrast to convergent and divergent boundaries, crust is cracked and broken at transform margins, but is not created or destroyed.
Virgin Islands. Home Ocean Exploration Facts What are the different types of plate tectonic boundaries? What are the different types of plate tectonic boundaries? There are three kinds of plate tectonic boundaries: divergent, convergent, and transform plate boundaries.The Earth's crust is a dynamic and evolving structure, a fact which is evident when earthquakes hit and volcanoes erupt.
For years scientists struggled to understand the Earth's movement. His theory was slammed by mainstream scientists at the time, but by the late s, his theory was thoroughly accepted.
It laid the groundwork for the modern day theory of plate tectonics; a theory that describes the Earth's crust as being made up of several plates. Today, those plates have been thoroughly studied and four types of tectonic plate boundaries, areas where the plates meet, have been described.
The currently held theory of how the continents on Earth came to be in their present locations is called the theory of plate tectonics. The theory states that the Earth's crust is made up of roughly 12 plates, sections of the Earth's crust that float upon the liquid rock mantle that lies just beneath it. While plate tectonics is based upon Wegener's theory of continental drift, the mechanism for plate movement was developed much later, and continues to be a field of active research to this day.
It is now understood that the force that moves the plates comes from the movement of the liquid mantle. Hot liquid rock rises up from deep within the Earth's core, cools as it reaches the surface, and sinks back down, creating giant circular convection belts.
Separate currents move the plates, resulting in the dynamic movement of the Earth's crust. Divergent plate boundaries occur where two plates are pulling away from each other. This results in what is known as a rift zone, an area defined by high volcanic activity.
As the plates pull apart from each other, new crust, in the form of liquid lava, is released from deep within the crust of the Earth. One famous rift zone on land is the Horn of Africa. Here, the horn is being pulled away from the rest of Africa, resulting in a deep rift, which at places has begun to fill in with water, forming large rift lakes. Another, the mid-Atlantic Ridge, is a deep underwater rift zone, where new oceanic crust is rising out of the rift, forming new ocean floor.
Both are sites of regular and intense volcanic activity. Convergent tectonic plate boundaries occur where two plates meet. In the case of a heavy ocean crust meeting a lighter continental plate, the oceanic crust is forced underneath the continental one. This creates a steep and very deep oceanic trench close to the continental shelf. High mountain ranges are associated with subduction zones. The Andes mountains of South America, for example, have been created, and continue to grow, due to the subduction of the Nazca oceanic plate under the continental South American plate.
However, if the convergent plate boundary is between two continental plates, neither is subducted.