The energy source for plate tectonics is Earth’s internal heat while the forces moving the plates are the “ridge push” and “slab pull” gravity forces. It was once thought that mantle convection . Friction between the converging plates and also the force required to bend a plate resist the movement of the plate at subduction zones. It seems likely that gravity drives the plates and the motions of the plates help to stir the mantle, rather than the convection of the mantle driving the plates.
Bythe idea that pieces of the Earth's surface moved how to get around captcha no longer seemed radical. The concepts of continental drift and seafloor spreading had revolutionized geology see our module The Origins of Plate Tectonic Theoryand scientists excitedly began to revise their interpretations of existing data into a comprehensive theory of plate tectonics.
For example, geologists had long recognized that earthquakes are not what is the reason for less bleeding during periods distributed on the Earth see Figure 1.
In fact, earthquakes are concentrated along the plate boundaries drawn by Harry Hess along mid-ocean ridges and subduction zones. Not all earthquakes occur at the same depth, however. What district do i live in florida Hess had postulated that the rocks of the ocean floor were diving down into subduction zonesearthquakes occur at shallow depths of 0 to 33 km below the surface near the trenches and at depths of almost km below the surface further inland illustrated in Figure 1 by different colored circles.
On the other hand, only shallow earthquakes depths of 0 to 33 km, shown in red what is meant by copyright Figure 1 are recorded at the spreading ridges. These data helped geologists draw more detailed cross-sections showing that plates are thin at spreading ridges, and that subduction extends long distances, taking plates deep beneath the continents.
Also similar to earthquakesdifferent kinds of volcanoes occur along different types of plate boundaries. Most of the volcanic eruptions that make the news, such as the Mount St. Helens eruption, take place near subduction zones. This type of volcano is represented by green triangles in Figure 2.
These devastating, explosive eruptions reflect the composition of the magma - it is extremely viscous what forces drive plate tectonic motion, or thick and resistant to flow, and thus results in tall, steep-sided volcanoes. In contrast, the volcanic eruptions that occur along spreading ridges are much gentler, in part because most of these eruptions occur under 2 to 3 kilometers of water, but also because the magma is far less viscous.
This type of volcano is represented by blue triangles in Figure 2. These observations about the distribution of earthquakes and volcanoes helped geologists define the processes that occur at spreading ridges and subduction zones. In addition, they helped scientists recognize that there are other types of plate boundaries. In general, plate boundaries are the scene of much geologic action - earthquakes, volcanoes, and dramatic topography such as mountain ranges like the Himalayas are all concentrated where two or more plates meet along a boundary.
There are three major ways that plates interact along boundaries: 1 They can move away from each other diverge2 they can move toward each other convergeor 3 they can move past each other, parallel to the boundary transform. Each of these interactions produces a different and characteristic pattern of earthquakesvolcanic activity, and topography.
The results of these interactions also depend on the type of crust involved, and there are two types of crust: oceanic and continental. Continental crust is thick and buoyant ; oceanic crust is thin, denseand forms at mid-ocean ridges. The most common divergent boundaries are the mid-ocean ridges that launched the plate tectonics revolution, and the Mid-Atlantic Ridge is a classic example see Figure 3.
Shallow earthquakes and minor basaltic lava flows characterize divergent boundaries at mid-ocean ridges. The seafloor at the ridges is higher than the surrounding plain because the rocks are hot and thus less dense and more buoyantriding higher in the underlying mantle. As the rocks move away from the spreading center, they cool and become more dense and less buoyant. Spreading has been occurring along the Mid-Atlantic Ridge for million years, resulting in a large ocean basin - the Atlantic Ocean.
Convergent boundaries are the most geologically active, with different features depending on the type of crust involved. The activity that takes place at convergent boundaries depends on the type of crust involved, as explained next. These are the subduction zones first imagined by Hess, where dense oceanic crust is diving beneath more buoyant continental crust. These boundaries are characterized by: a a very deep ocean trench next to a high continental mountain range, b large numbers of earthquakes that progress from shallow to deep, and c large numbers of intermediate composition volcanoes see Figure 4.
The Andes owe their existence to a subduction zone on the western edge of the South American plate; in fact, this type of boundary is often called an Andean boundary since it is the primary example.
Where two plates converge along a boundary where the crust on both sides is oceanic, a subduction zone also occurs, but the result is slightly different than an Andean margin.
Since the densities of the two plates are similar, it is usually the plate with the older oceanic crust that is subducted because that crust is colder and denser. Earthquakes progress from shallow to deep, moving away from the trench like in the oceanic-continental convergence, and volcanoes form an island arc, like the mountain range along the Tonga trench in the western Pacific see How to copy playstation cd 5.
When two pieces of continental crust converge, the result is a great pileup of continental material. Both pieces of crust are buoyant and are not easily subducted. Continental convergence is exemplified by the Himalayan mountain range, where the Indian plate runs into the Asian plate see Figure 6. Numerous shallow earthquakes occur, but there is very little volcanism.
Most boundaries are either convergent or divergent, but transform boundaries occur in a few places to accommodate lateral motion, where plates move horizontally past one another. This type of how to replace a bathroom toilet is very rare on continents, but they are dramatic where they do occur.
For example, the San Andreas Fault in California is a continental transform boundary. Along this boundary, frequent, shallow earthquakes occur like the famous and San Francisco earthquakesbut there is little associated volcanic activity or topographic relief see Figure 7.
The Alpine Fault in New Zealand is very similar. Most transform what forces drive plate tectonic motion occur not on land, however, but in short segments along mid-ocean ridges. A few boundaries defy simple classification and are referred to as "plate boundary zones. The plate boundaries described above account for the vast majority of seismic and volcanic activity on Earth.
The more data that began to fit into the plate tectonics scheme, however, the more the exceptions stood out.
What could account for Hawaii, for example, a scene of long-lived volcanic activity in the middle of the Pacific plate where there is no subduction or spreading to generate magma?
There had to be something else. InJ. Tuzo Wilsona Canadian geophysicist, theorized that the mantle contained immobile hotspotsthin plumes of hot magma that acted like Bunsen burners as plates moved over them Wilson, The Hawaiian Islands form a long, linear chain, with ongoing volcanic eruptions on the island of Hawaii and extincthighly eroded volcanic islands to the northwest. According to Wilson's hotspot theorythe chain of islands represents the northwestward motion of the Pacific plate over a mantle plume.
One important implication of Wilson's theory was that because hotspots were stationary, hotspot tracks could be used to trace plate motion history. For example, the track of the Hawaiian chain continues to the northwest as an underwater chain of progressively older, no longer active volcanoes. Once the volcanic eruptions stop, ocean waves begin to take their toll, eroding the islands down to just below sea level, at which point they are called seamounts.
The islands and seamounts associated with the Hawaiian hotspot provide a history of motion for the Pacific plate, which appears to have taken an eastward turn around 42 million years ago see Figure Other hotspot tracks around the world can be used in a similar manner to reconstruct a global plate tectonic history. According to Wilson, hotspots can be used to track the history of plate motion because the hotspots are.
Hotspots added further proof to confirm that plates move constantly and steadily. Ironically, however, the question that incited ridicule for Wegener continues to launch heated debate today: What ultimately drives plate motion? Plates are constantly shifting and rearranging themselves in response what is self help book each other. Eventually, a new Pangaea or single supercontinent will form, break apart, and form again on Earth.
What keeps these plates moving? Hess assumed that mantle convection was the main driving force - hot, less dense material rises along mid-ocean ridgescools, and subsides at subduction zones, and the plates "ride" these convection cells see our Density module for more information.
Though there is little doubt that convection does occur in the mantle, current modeling suggests that it is not so simple. Many geologists argue that the force of convection is not enough to push enormous lithospheric plates like the North American plate. They suggest instead that gravity is the main driving force: Cold, dense oceanic crust sinks at subduction zonespulling the rest of the plate with it.
According to this theorymagmatic intrusions at spreading ridges are passive - the magma merely fills a hole created by pulling two plates apart. Undoubtedly, gravity and convection both supply energy to keep plates moving. Their relative contributions, however, are a matter of debate and ongoing research. The strength of plate tectonic theory lies in its ability to explain everything about the processes we see both in the geologic record and in the present.
Our understanding of the subtleties continues to evolve as we learn more about our planet, but what is gross pay and net pay tectonics is truly the foundation upon which the science of geology is built.
Earthquakes and volcanoes can reveal a lot about plate boundaries. This module looks at the nature of tectonic plates and discusses the different boundary types that exist between them — convergent, divergent, and transform.
Forces that drive the push and pull of these landmasses are explored. Earthquakes and volcanoes occur primarily along plate boundaries; the frequency and type of events vary with the type of boundary. Plates interact with one another at boundaries in one of three ways: they diverge, converge, or slide past one another. Plates are made up of two types of crust — oceanic and continental; oceanic crust is thinner and denser than continental crust. A single plate can have both continental and oceanic crust.
Reading Quiz Resources. Bookmark Glossary Terms Bythe idea that pieces of the Earth's surface moved around no longer seemed radical. Figure 1. Map showing earthquakes from with magnitude greater than 3. Data are from the Advanced National Seismic System. Egger In fact, earthquakes are concentrated along the plate boundaries drawn by Harry Hess along mid-ocean ridges and subduction zones. Similar to earthquakesvolcanoes are located preferentially on or near plate boundaries see Figure 2.
Figure 2. Map showing volcanoes that have been active in the last 10, years. Colored triangles indicate different volcano types: Red triangles are primarily calderas; green triangles are stratovolcanoes; blue triangles are shield volcanoes and fissure vents. Egger Also similar to earthquakesdifferent kinds of volcanoes occur along different types of plate boundaries.
Comprehension Checkpoint Divergent boundaries are most common a. Comprehension Checkpoint Along convergent plate boundaries there are always big volcanoes. Comprehension Checkpoint According to Wilson, hotspots can be used to track the what forces drive plate tectonic motion of plate motion because the hotspots are a.
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It is generally accepted that tectonic plates are able to move because of the relative density of oceanic lithosphere and the relative weakness of the asthenosphere. Dissipation of heat from the mantle is acknowledged to be the original source of the energy required to drive plate tectonics through convection or large scale upwelling and doming. The subducting plate, usually basalt, is denser than the material it is subducting into, purely due to its difference in temperature. As the plate sinks into the mantle, it acts to pull the rest of the plate behind it. This force is considered by some to be the primary force . Click to see full answer Also, what are the forces that drive plate motion? The forces that drive Plate Tectonics include: Convection in the Mantle (heat driven) Ridge push (gravitational force at the spreading ridges) Slab pull (gravitational force in subduction zones).
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Lithospheric plates are part of a planetary scale thermal convection system. It was once thought that mantle convection could drive plate motions. Early textbooks showed mantle convection cells, like in a beaker of hot liquid on a Bunsen burner, pushing plates along from below. What would cause that? Current dynamic models have plates moving as part of a gravity-driven convection system that pushes young hot plates away from spreading ridges and pulls old cold plates down into subduction zones.
Use appropriate media player to utilize captioning. People often use the terms crust and tectonic plates interchangeably. It can be confusing because they are paired, and yet they are distinct from each other. Please click here if you are not redirected within a few seconds. IRIS ingests, curates, and distributes geoscience data IRIS provides management of, and access to, observed and derived data for the global earth science community. This includes ground motion, atmospheric, infrasonic, hydrological, and hydroacoustic data.
IRIS provides a wide range of education and outreach resources Our mission is to advance awareness and understanding of seismology and earth science while inspiring careers in geophysics. IRIS operates many prominent geophysical facilities IRIS staff and subawardees oversee the construction, operation, and maintenance of seismic networks and related data facilities utilized by a wide sector of the earth science community.
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Home InClass Animation What are the forces that drive plate tectonics. Animation Closed Captioning. Your browser does not support the video tag. The forces that drive Plate Tectonics include: Convection in the Mantle heat driven Ridge push gravitational force at the spreading ridges Slab pull gravitational force in subduction zones. Related Animations Take 2: Plate vs. Animation Novice.