Who first proposed the idea of plate tectonics?
German meteorologist Alfred Wegener is often credited as the first to develop a theory of plate tectonics, in the form of continental drift. Bringi...
What is the cause of plate tectonics?
Although this has yet to be proven with certainty, most geologists and geophysicists agree that plate movement is caused by the convection (that is...
What is the Ring of Fire, and where is it?
The Ring of Fire is a long horseshoe-shaped earthquake-prone belt of volcanoes and tectonic plate boundaries that fringes the Pacific Ocean basin....
Why are there tectonic plates?
Earth’s hard surface (the lithosphere) can be thought of as a skin that rests and slides upon a semi-molten layer of rock called the asthenosphere....
When did plate tectonics begin?
'pertaining to building') is a scientific theory describing the large-scale motion of the plates making up the Earth 's lithosphere since tectonic processes began on Earth between 3.3 and 3.5 billion years ago.
Why do tectonic plates move?
It has generally been 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 current view, though still a matter of some debate, asserts that as a consequence, a powerful source generating plate motion is the excess density of the oceanic lithosphere sinking in subduction zones. When the new crust forms at mid-ocean ridges, this oceanic lithosphere is initially less dense than the underlying asthenosphere, but it becomes denser with age as it conductively cools and thickens. The greater density of old lithosphere relative to the underlying asthenosphere allows it to sink into the deep mantle at subduction zones, providing most of the driving force for plate movement. The weakness of the asthenosphere allows the tectonic plates to move easily towards a subduction zone. Although subduction is thought to be the strongest force driving plate motions, it cannot be the only force since there are plates such as the North American Plate which are moving, yet are nowhere being subducted. The same is true for the enormous Eurasian Plate. The sources of plate motion are a matter of intensive research and discussion among scientists. One of the main points is that the kinematic pattern of the movement itself should be separated clearly from the possible geodynamic mechanism that is invoked as the driving force of the observed movement, as some patterns may be explained by more than one mechanism. In short, the driving forces advocated at the moment can be divided into three categories based on the relationship to the movement: mantle dynamics related, gravity related (main driving force accepted nowadays), and earth rotation related.
What is the t. e. diagram of the internal layering of Earth showing the lithosphere above?
t. e. Diagram of the internal layering of Earth showing the lithosphere above the asthenosphere (not to scale) Plate tectonics (from the Late Latin: tectonicus, from the Ancient Greek: τεκτονικός, lit. 'pertaining to building') is a scientific theory describing the large-scale motion of the plates making up the Earth 's lithosphere ...
Why is Venus not tectonic?
One explanation for Venus's lack of plate tectonics is that on Venus temperatures are too high for significant water to be present. Earth's crust is soaked with water, and water plays an important role in the development of shear zones. Plate tectonics requires weak surfaces in the crust along which crustal slices can move, and it may well be that such weakening never took place on Venus because of the absence of water. However, some researchers remain convinced that plate tectonics is or was once active on this planet.
How many major plates are there in the lithosphere?
Earth's lithosphere is composed of seven or eight major plates (depending on how they are defined) and many minor plates. Where the plates meet, their relative motion determines the type of boundary: convergent, divergent, or transform. Earthquakes, volcanic activity, mountain -building, and oceanic trench formation occur along these plate boundaries (or faults ). The relative movement of the plates typically ranges from zero to 100 mm annually.
Which tectonics group proposed that the oceanic crust be in motion with the continents?
However, in the plate tectonics context (accepted since the seafloor spreading proposals of Heezen, Hess, Dietz, Morley, Vine, and Matthews (see below) during the early 1960s), the oceanic crust is suggested to be in motion with the continents which caused the proposals related to Earth rotation to be reconsidered. In more recent literature, these driving forces are:
What is a convergent boundary?
Convergent boundaries (Destructive) (or active margins) occur where two plates slide toward each other to form either a subduction zone (one plate moving underneath the other) or a continental collision.
What is a tectonic plate?
A tectonic plate (also called lithospheric plate) is a massive, irregularly shaped slab of solid rock, generally composed of both continental and oceanic lithosphere. Plate size can vary greatly, from a few hundred to thousands of kilometers across; the Pacific and Antarctic Plates are among the largest. Plate thickness also varies greatly, ranging ...
Why can't we see the boundaries of plates?
Most of the boundaries between individual plates cannot be seen, because they are hidden beneath the oceans. Yet oceanic plate boundaries can be mapped accurately from outer space by measurements from GEOSAT satellites. Earthquake and volcanic activity is concentrated near these boundaries.
What is the difference between continental and oceanic crust?
The answer lies in the composition of the rocks. Continental crust is composed of granitic rocks which are made up of relatively lightweight minerals such as quartz and feldspar. By contrast, oceanic crust is composed of basaltic rocks, which are much denser and heavier.
Why is the crust under the oceans thicker than the crust under the continents?
Because continental rocks are much lighter, the crust under the continents is much thicker (as much as 100 km) whereas the crust under the oceans is generally only about 5 km thick.
Where is the oceanic lithosphere sinking?
This process is happening now off the coast of Oregon and Washington.
How thick is the lithosphere?
Plate thickness also varies greatly, ranging from less than 15 km for young oceanic lithosphere to about 200 km or more for ancient continental lithosphere (for example, the interior parts of North and South America).
Which plate is the most tectonic?
Indo-Australian Plate – A major tectonic plate formed by the fusion of the Indian and Australian plates – 58,900,000 km 2 often considered two plates: Australian Plate – Major tectonic plate, originally a part of the ancient continent of Gondwana – 47,000,000 km 2.
Which plate contains the continent of Antarctica?
Antarctic Plate – Tectonic plate containing the continent of Antarctica and extending outward under the surrounding oceans – 60,900,000 km 2. Eurasian Plate – Tectonic plate which includes most of the continent of Eurasia – 67,800,000 km 2.
How many tectonic plates are there in the lithosphere?
List of the relatively moving sections of the lithosphere of Earth. Map showing Earth's lithosphere divided into 15 principal tectonic plates. Plate tectonics map from NASA. This is a list of tectonic plates on Earth's surface. Tectonic plates are pieces of Earth's crust and uppermost mantle, together referred to as the lithosphere.
What is the name of the plate that is sandwiched between the Cocos Plate and Nazca Plate?
Caribbean Plate. Panama Plate – A small tectonic plate sandwiched between the Cocos Plate and Nazca Plate to the south and the Caribbean Plate to the north. Gonâve Microplate – Part of the boundary between the North American Plate and the Caribbean Plate. South Jamaica Microplate.
What is the North American plate?
North American Plate – Large tectonic plate including most of North America, Greenland and part of Siberia. – 75,900,000 km 2
What is the name of the plate that is located off the west coast of Mexico?
Rivera Plate – Small tectonic plate off the west coast of Mexico. Eurasian Plate. Adriatic Plate, also known as Apulian Plate – A small tectonic plate in the Mediterranean. Aegean Sea Plate, also known as Hellenic Plate – A small tectonic plate in the eastern Mediterranean Sea.
What is a minor plate?
For purposes of this list, a minor plate is any plate with an area less than 20 million km 2 but greater than 1 million km 2 .
What is plate tectonics?
Plate tectonics, theory dealing with the dynamics of Earth ’s outer shell—the lithosphere — that revolutionized Earth sciences by providing a uniform context for understanding mountain-building processes, volcanoes, and earthquakes as well as the evolution of Earth’s surface and reconstructing its past continents and oceans.
How do plates move?
Although this has yet to be proven with certainty, most geologists and geophysicists agree that plate movement is caused by the convection (that is, heat transfer resulting from the movement of a heated fluid) of magma in Earth’s interior. The heat source is thought to be the decay of radioactive elements. How this convection propels the plates is poorly understood. Some geologists argue that upwelling magma at spreading centres pushes the plates, whereas others argue that the weight of a portion of a subducting plate (one that is forced beneath another) may pull the rest of the plate along.
How do plates cause mountains to rise?
Plate motions cause mountains to rise where plates push together, or converge, and continents to fracture and ocean s to form where plates pull apart, or diverge. The continents are embedded in the plates and drift passively with them, which over millions of years results in significant changes in Earth’s geography.
What is the lithosphere?
Earth's lithosphere and upper mantle. A cross section of Earth's outer layers, from the crust through the lower mantle. Encyclopædia Britannica, Inc. The process of plate tectonics may be driven by convection in Earth’s mantle, the pull of heavy old pieces of crust into the mantle, or some combination of both.
What are the processes that shape the Earth's surface?
While the interiors of the plates are presumed to remain essentially undeformed, plate boundaries are the sites of many of the principal processes that shape the terrestrial surface, including earthquakes, volcanism, and orogeny (that is, formation of mountain ranges). Earth's lithosphere and upper mantle.
Why are plates moving?
Plate movement is possible because the lithosphere-asthenosphere boundary is a zone of detachment. As the lithospheric plates move across Earth’s surface, driven by forces as yet not fully understood, they interact along their boundaries, diverging, converging, or slipping past each other.
How does plate tectonics affect the Earth's atmosphere?
During the late 20th and early 21st centuries, it became apparent that plate-tectonic processes profoundly influence the composition of Earth’s atmosphere and oceans, serve as a prime cause of long-term climate change, and make significant contributions to the chemical and physical environment in which life evolves.
How many major tectonic plates are there?
Here are the 7 major tectonic plates of the world in a bit more detail.
Why are tectonic plates unusual?
Earth’s tectonic plate boundaries are unusual because they can consist of continent and ocean crust. Here are the 7 major tectonic plates of the world in a bit more detail. 1.
What is the Eurasian plate?
The Eurasian major plate consists of most of Europe, Russia, and parts of Asia. This plate is sandwiched between the North American and African Plates on the north and west sides. The west side has a divergent boundary with the North American plate.
Why does South America have earthquakes?
At the west side of South America, it experiences devastating earthquakes due to the convergent plate tectonic boundaries.
Which plate covers the entire continent of Antarctica?
Antarctic Plate . The Antarctic plate holds the entire continent of Antarctica including its surround oceanic crust. This plate is surrounded by parts of the African, Australian, Pacific, and South American plates. Antarctica was once grouped as part of the supercontinent Gondwana with Australia and India.
How fast does the Eurasian plate move?
On average, the Eurasian plate moves about one-quarter to half an inch per year.
What is the North American plate?
It also includes Greenland, Cuba, and the Bahamas. The interior of the North American plate contains a giant granitic craton. It’s believed that the North American (Laurentian) craton is 4 billion years old.
What are the boundaries of the Earth's plates?
The edges of Earth's lithospheric plates have boundaries which are both well defined and poorly defined. Well-defined boundaries include mid-ocean ridges and ocean trenches. These boundaries are usually well enough defined that they can be plotted on a map at a reasonably accurate location.
What is the divergent boundary between the North America and the Eurasian plates?
The boundary between the North America Plate and the Eurasian Plate is an example of a divergent boundary at a mid-ocean ridge. All of the plate boundaries that occur down the center of the Atlantic Ocean are divergent boundaries that follow the crest of the Mid-Atlantic Ridge. Map showing the geographic location of major ocean trenches in ...
What is the outermost part of the Earth's structure?
Earth's Major Tectonic Plates. The outermost part of Earth's structure is known as the lithosphere. The lithosphere consists of the crust and small portion of the upper mantle. The lithosphere is divided into a number of tectonic plates.
Where do ocean trenches form?
Ocean trenches form where a plate with a leading edge of oceanic lithosphere collides with another plate. In these situations, an oceanic plate normally subducts into the mantle, forming a topographic low on the ocean floor. The point on the seafloor where the colliding plates are in contact is normally considered to be the geographic location of the plate boundary.
What is the outer shell of Earth made of?
According the theory of plate tectonics, Earth's outer shell is made up of a series of plates. The map above shows names and generalized locations of Earth's major tectonic plates. These plates move and interact with one another to produce earthquakes, volcanoes, mountain ranges, ocean trenches and other geologic processes and features.
Overview
Plate tectonics (from the Late Latin: tectonicus, from the Ancient Greek: τεκτονικός, lit. 'pertaining to building') is the generally accepted scientific theory that considers the Earth's lithosphere to comprise a number of large tectonic plates which have been slowly moving since about 3.4 billion years ago. The model builds on the concept of continental drift, an idea developed during the f…
Key principles
The outer layers of Earth are divided into the lithosphere and asthenosphere. The division is based on differences in mechanical properties and in the method for the transfer of heat. The lithosphere is cooler and more rigid, while the asthenosphere is hotter and flows more easily. In terms of heat transfer, the lithosphere loses heat by conduction, whereas the asthenosphere also transfers heat by convection and has a nearly adiabatic temperature gradient. This division should not be confus…
Types of plate boundaries
Three types of plate boundaries exist, with a fourth, mixed type, characterized by the way the plates move relative to each other. They are associated with different types of surface phenomena. The different types of plate boundaries are:
• Divergent boundaries (constructive boundaries or extensional boundaries) oc…
Driving forces of plate motion
It has generally been 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 current view, though still …
History of the theory
Italian polymath Leonardo da Vinci was the first to theorize that mountains gradually rise from the oceans, explaining why they have fossils of marine life.
Around the start of the twentieth century, various theorists unsuccessfully attempted to explain the many geographical, geological, and biological continuities between continents. In 1912 the meteorologist Alfred Wegener des…
Implications for biogeography
Continental drift theory helps biogeographers to explain the disjunct biogeographic distribution of present-day life found on different continents but having similar ancestors. In particular, it explains the Gondwanan distribution of ratites and the Antarctic flora.
Plate reconstruction
Reconstruction is used to establish past (and future) plate configurations, helping determine the shape and make-up of ancient supercontinents and providing a basis for paleogeography.
Current plate boundaries are defined by their seismicity. Past plate boundaries within existing plates are identified from a variety of evidence, such as the presence of ophiolites that are indicative of vanished oceans.
Current plates
Depending on how they are defined, there are usually seven or eight "major" plates: African, Antarctic, Eurasian, North American, South American, Pacific, and Indo-Australian. The latter is sometimes subdivided into the Indian and Australian plates.
There are dozens of smaller plates, the seven largest of which are the Arabian, Caribbean, Juan de Fuca, Cocos, Nazca, Philippine Sea, and Scotia.
Overview
This is a list of tectonic plates on Earth's surface. Tectonic plates are pieces of Earth's crust and uppermost mantle, together referred to as the lithosphere. The plates are around 100 km (62 mi) thick and consist of two principal types of material: oceanic crust (also called sima from silicon and magnesium) and continental crust (sial from silicon and aluminium). The composition of the two …
Current plates
Geologists generally agree that the following tectonic plates currently exist on Earth's surface with roughly definable boundaries. Tectonic plates are sometimes subdivided into three fairly arbitrary categories: major (or primary) plates, minor (or secondary) plates, and microplates (or tertiary plates).
These plates comprise the bulk of the continents and the Pacific Ocean. For pu…
Ancient continental formations
In the history of Earth many tectonic plates have come into existence and have over the intervening years either accreted onto other plates to form larger plates, rifted into smaller plates, or have been crushed by or subducted under other plates.
Supercontinent – Landmass comprising more than one continental core, or cra…
See also
• Asthenosphere – Highly viscous, mechanically weak and ductile region of Earth's mantle
• Continent – Very large landmass identified by convention
• Craton – Old and stable part of the continental lithosphere
External links
• Bird, Peter (2003) An updated digital model of plate boundaries also available as a large (13 Mb) PDF file