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J. Tuzo Wilson

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What we Learn in the Past, Present, and Future Studying Plate Tectonics

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What we Learn in the Past, Present, and Future Studying Plate Tectonics

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We can learn about our world in the past, present and the future by studying the theory of Plate Tectonics because of finger nail growth the plate are moving at different speeds constantly and the jigsaw changes with it.

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The History of The Theory of Plate Tectonics

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The History of The Theory of Plate Tectonics

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Alfred Wagener as a German scientist who created the theory of continental drift, but had many thoughts before. In 1915 Wegener said the only possible answer is continental drift. He thought this cause because continental drift stated converging plates. Wegener tried to prove his point by saying he saw the " jigsaw" fit between South America and Arica with there three other points. It is likely that convection currents caused by the unequal distribution of heat within earths core because the plates move.
Earthquakes and volcanos are created by plate tectonics and happen mostly around the ring of fire. No one fully understands the forces that cause the plates to move.

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The Theory of Plate Tectonics was created about 300 million years ago. The moving land masses came together to form the supercontinent of pangaea which means " all lands". J. Tuzo Wilson was the one to create the the theory. Plate tectonics is the theory that Earth's outer shell is divided into several plates that glide over the rocky inner layer above the core.

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The Ring of Fire is the result of plate tectonics. Tectonic plates are slabs of the Earth’s crust, which fit together like pieces of a puzzle that can shift.
This website's main focus is the Ring of Fire which is very important when it comes to the Theory and includes a picture of where it is located.

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This website's main focus is how the plates move, how far they go and where they are located.
This website explains more scientific facts near the end of the article.
This website is important because it focuses on the scientific part of the Theory of Plate Tectonics.

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This website focuses on the background of the Theory of Plate Tectonics and how it originated and evolved.
It's explaining how the theory originated. Alfred Wegener is a German scientist that stated that the only possible answer was continental drift. The article explains a lot of his input on the Theory of Plate Tectonics.
The importance of this website helps the reader get facts about not only what Plate Tectonics is but how it was originated and its theory.

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Plate Tectonics: The Rocky History of an Idea

Close examination of a globe often results in the observation that most of the continents seem to fit together like a puzzle: the west African coastline seems to snuggle nicely into the east coast of South America and the Caribbean sea; and a similar fit appears across the Pacific. The fit is even more striking when the submerged continental shelves are compared rather than the coastlines. In 1912 Alfred Wegener (1880-1930) noticed the same thing and proposed that the continents were once compressed into a single protocontinent which he called Pangaea (meaning "all lands"), and over time they have drifted apart into their current distribution. He believed that Pangaea was intact until the late Carboniferous period, about 300 million years ago, when it began to break up and drift apart. However, Wegener's hypothesis lacked a geological mechanism to explain how the continents could drift across the earths surface as he proposed.

Searching for evidence to further develop his theory of continental drift, Wegener came across a paleontological paper suggesting that a land bridge had once connected Africa with Brazil. This proposed land bridge was an attempt to explain the well known paleontological observation that the same fossilized plants and animals from the same time period were found in South America and Africa. The same was true for fossils found in Europe and North America, and Madagascar and India. Many of these organisms could not have traveled across the vast oceans that currently exist. Wegener's drift theory seemed more plausible than land bridges connecting all of the continents. But that in itself was not enough to support his idea. Another observation favoring continental drift was the presence of evidence for continental glaciation in the Pensylvanian period. Striae left by the scraping of glaciers over the land surface indicated that Africa and South America had been close together at the time of this ancient ice age. The same scraping patterns can be found along the coasts of South America and South Africa.

Wegener's drift hypothesis also provided an alternate explanation for the formation of mountains (orogenesis). The theory being discussed during his time was the "Contraction theory" which suggested that the planet was once a molten ball and in the process of cooling the surface cracked and folded up on itself. The big problem with this idea was that all mountain ranges should be approximately the same age, and this was known not to be true. Wegener's explanation was that as the continents moved, the leading edge of the continent would encounter resistance and thus compress and fold upwards forming mountains near the leading edges of the drifting continents. The Sierra Nevada mountains on the Pacific coast of North America and the Andes on the coast of South America were cited. Wegener also suggested that India drifted northward into the asian continent thus forming the Himalayas.

Wegener eventually proposed a mechanism for continental drift that focused on his assertion that the rotation of the earth created a centrifugal force towards the equator. He believed that Pangaea originated near the south pole and that the centrifugal force of the planet caused the protocontinent to break apart and the resultant continents to drift towards the equator. He called this the "pole-fleeing force". This idea was quickly rejected by the scientific community primarily because the actual forces generated by the rotation of the earth were calculated to be insufficient to move continents. Wegener also tried to explain the westward drift of the Americas by invoking the gravitational forces of the sun and the moon, this idea was also quickly rejected. Wegener's inability to provide an adequate explanation of the forces responsible for continental drift and the prevailing belief that the earth was solid and immovable resulted in the scientific dismissal of his theories.

In 1929, about the time Wegener's ideas began to be dismissed, Arthur Holmes elaborated on one of Wegener's many hypotheses; the idea that the mantle undergoes thermal convection. This idea is based on the fact that as a substance is heated its density decreases and rises to the surface until it is cooled and sinks again. This repeated heating and cooling results in a current which may be enough to cause continents to move. Arthur Holmes suggested that this thermal convection was like a conveyor belt and that the upwelling pressure could break apart a continent and then force the broken continent in opposite directions carried by the convection currents. This idea received very little attention at the time.

Not until the 1960's did Holmes' idea receive any attention. Greater understanding of the ocean floor and the discoveries of features like mid-oceanic ridges, geomagnetic anomalies parallel to the mid-oceanic ridges, and the association of island arcs and oceanic trenches occurring together and near the continental margins, suggested convection might indeed be at work. These discoveries and more led Harry Hess (1962) and R.Deitz (1961) to publish similar hypotheses based on mantle convection currents, now known as "sea floor spreading". This idea was basically the same as that proposed by Holmes over 30 years earlier, but now there was much more evidence to further develop and support the idea. To learn more about the current theories which describe the mechanisms behind continental drift go to the "Plate Tectonics: The Mechanism" page.
To learn more about plate tectonics, read the books I used as references listed below:

The New View of the Earth by Seiya Uyeda, 1978 by W.H. Freeman and Co.

The Earth's Dynamic Systems by W. Kenneth Hamblin, 1975 by Burgess Publishing Co.

Global Tectonics by Philip Kearey & Frederick J. Vine, 1996 by Blackwell Sciences Ltd.

Physical Geology by Carla W. Montgomery, 1987 by Wm. C. Brown Publishers.

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Plate Tectonics: The Rocky History of an Idea Close examination of a globe often results in the observation that most of the continents seem to fit together like a puzzle: the west African coastline seems to snuggle nicely into the east coast of South America and the Caribbean sea; and a similar fit appears across the Pacific.

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This website mainly focuses on what plate tectonics is and how it was found.
This website explains the theory more in the beginning of the article. The first paragraph includes a map that shows the different plate tectonics of the earth, which provides an explanation on the plates further on in the website.
This website is very informative on  the theory of plate tectonics and background knowledge on how it was found.
The importance of this website is that it helps the reader find  very self explanatory information on plate tectonics and the theory of it.

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Tectonic plates of the Earth.

Credit: USGS

From the deepest ocean trench to the tallest mountain, plate tectonics explains the features and movement of Earth's surface in the present and the past.

Plate tectonics is the theory that Earth's outer shell is divided into several plates that glide over the mantle, the rocky inner layer above the core. The plates act like a hard and rigid shell compared to Earth's mantle. This strong outer layer is called the lithosphere, which is 100 km (60 miles) thick, according to Encyclopedia Britannica. The lithosphere includes the crust and outer part of the mantle. Below the lithosphere is the asthenosphere, which is malleable or partially malleable, allowing the lithosphere to move around. How it moves around is an evolving idea.

Developed from the 1950s through the 1970s, plate tectonics is the modern version of continental drift, a theory first proposed by scientist Alfred Wegener in 1912. Wegener didn't have an explanation for how continents could move around the planet, but researchers do now. Plate tectonics is the unifying theory of geology, said Nicholas van der Elst, a seismologist at Columbia University's Lamont-Doherty Earth Observatory in Palisades, New York.

"Before plate tectonics, people had to come up with explanations of the geologic features in their region that were unique to that particular region," Van der Elst said. "Plate tectonics unified all these descriptions and said that you should be able to describe all geologic features as though driven by the relative motion of these tectonic plates."

There are nine major plates, according to World Atlas. These plates are named after the landforms found on them. The nine major plates are North American, Pacific, Eurasian, African, Indo-Australian, Australian, Indian, South American and Antarctic.

The largest plate is the Pacific Plate at 39,768,522 square miles (103,000,000 square kilometers). Most of it is located under the ocean. It is moving northwest at a speed of around 2.75 inches (7 cm) per year.

There are also many smaller plates throughout the world.

The driving force behind plate tectonics is convection in the mantle. Hot material near the Earth's core rises, and colder mantle rock sinks. "It's kind of like a pot boiling on a stove," Van der Elst said. The convection drive plates tectonics through a combination of pushing and spreading apart at mid-ocean ridges and pulling and sinking downward at subduction zones, researchers think. Scientists continue to study and debate the mechanisms that move the plates.

Mid-ocean ridges are gaps between tectonic plates that mantle the Earth like seams on a baseball. Hot magma wells up at the ridges, forming new ocean crust and shoving the plates apart. At subduction zones, two tectonic plates meet and one slides beneath the other back into the mantle, the layer underneath the crust. The cold, sinking plate pulls the crust behind it downward.

Many spectacular volcanoes are found along subduction zones, such as the "Ring of Fire" that surrounds the Pacific Ocean.

Subduction zones, or convergent margins, are one of the three types of plate boundaries. The others are divergent and transform margins.

At a divergent margin, two plates are spreading apart, as at seafloor-spreading ridges or continental rift zones such as the East Africa Rift.

Transform margins mark slip-sliding plates, such as California's San Andreas Fault, where the North America and Pacific plates grind past each other with a mostly horizontal motion.

While the Earth is 4.54 billion years old, because oceanic crust is constantly recycled at subduction zones, the oldest seafloor is only about 200 million years old. The oldest ocean rocks are found in the northwestern Pacific Ocean and the eastern Mediterranean Sea. Fragments of continental crust are much older, with large chunks at least 3.8 billion years found in Greenland.

With clues left behind in rocks and fossils, geoscientists can reconstruct the past history of Earth's continents. Most researchers think modern plate tectonics began about 3 billion years ago, based on ancient magmas and minerals preserved in rocks from that period. Some believe it could have started a billion years after Earth's birth, at around 3.5 billion years.

"We don't really know when plate tectonics as it looks today got started, but we do know that we have continental crust that was likely scraped off a down-going slab [a tectonic plate in a subduction zone] that is 3.8 billion years old," Van der Elst said. "We could guess that means plate tectonics was operating, but it might have looked very different from today."

As the continents jostle around the Earth, they occasionally come together to form giant supercontinents, a single landmass. One of the earliest big supercontinents, called Rodinia, assembled about 1 billion years ago. Its breakup is linked to a global glaciation called Snowball Earth.

A more recent supercontinent called Pangaea formed about 300 million years ago. Africa, South America, North America and Europe nestled closely together, leaving a characteristic pattern of fossils and rocks for geologists to decipher once Pangaea broke apart. The puzzle pieces left behind by Pangaea, from fossils to the matching shorelines along the Atlantic Ocean, provided the first hints that the Earth's continents move.

Plates bumping into each other can also cause mountain ranges. For example, India and Asia came together about 55 million years ago, which created the Himalaya Mountains, according to National Geographic.

In the 20th century, researchers realized that the Earth's crust is not one piece, but is made up of many huge tectonic plates upon which the continents ride.

Credit: by Karl Tate, Infographics Artist

Additional reporting by Alina Bradford, Live Science contributor

Additional resources

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From the deepest ocean trench to the tallest mountain, plate tectonics explains the features and movement of Earth's surface in the present and the past. Plate tectonics is the theory that Earth's outer shell is divided into several plates that glide over the mantle, the rocky inner layer above the core.