BCEarth sciences 11 (June 201811Big Idea: plate Tectonic Theory defines the consequences of tectonic plate interactions.

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BCGeology 12 (June 2018)12Big Idea: The plate tectonic theory defines the alters that take place within Earth and also to earth crust throughout geological time.
BCScience great 8 (June 2016)8Big Idea: The concept of plate tectonics is the unifying concept that defines Earth’s geology processes.
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Learn about the theory of continental Drift and Plate Tectonics and also discover what happens as soon as plates collide!

Continental Drift and Plate Tectonics

Continental Drift

Today, most human being know the landmasses on earth move around, however people haven’t always believed this. The wasn’t till the beforehand 20th century that German scientist Alfred Wegener put soon the idea that the earth continents were drifting. He called this movement Continental Drift. The was not the first or only human to think this, but he was the first to talk about the idea publicly.

Wegener come up through this idea due to the fact that he noticed the the coastlines of western Africa and also eastern southern America looked prefer puzzle pieces, which could have when fit together and also then drifted apart. Feather at every one of the continent he theorized the they had actually once been joined together as a supercontinent (which was later on called Pangaea) around 225 million years ago (see figure 4). The name Pangaea originates from the old Greek indigenous “pan,” meaning entire, and “Gaia,” meaning Earth. Pangaea is no the just supercontinent believed to have existed. Larger supercontinents are additionally believed to have actually come prior to Pangaea.


Movement the tectonic key (Source: U.S. Geological Survey).

The idea of moving landmasses seems evident now, but Wegener’s Theory of continent Drift (as he dubbed it) to be not embraced for countless years. Why? Well, for one thing, Wegener go not have actually a convincing explanation because that the reason of the drifting (he argued that the continents to be moving about due to the earth rotation, which later turned out to be wrong). Secondly, he was a meteorologist (someone who studies weather), no a geologist, for this reason geologists no think that knew what the was talk about. 

Fossil Evidence

One form of proof that strongly sustained the concept of continental Drift is the fossil record. Fossils of similar types that plants and also animals in rocks of a similar age have been uncovered on the shores of different continents, suggesting that the continent were when joined. For example, fossils of Mesosaurus, a freshwater reptile, have been discovered both in Brazil and also western Africa. Also, fossils the the floor reptile Lystrosaurus have been uncovered in rocks of the same period in Africa, India and Antarctica.


Map of fossil proof (Source: Osvaldocangaspadilla via Wikimedia Commons).


Plate Tectonics

The Theory of plate Tectonics builds ~ above Wegener’s theory of continent Drift. In the theory of bowl Tectonics, it is tectonic plates, fairly than continents, which are moving.

Tectonic plates are pieces of the lithosphere and also crust, which float on the asthenosphere. There space currently seven plates that comprise most of the continents and the Pacific Ocean. Lock are:

African PlateAntarctic PlateEurasian PlateIndo-Australian PlateNorth American PlatePacific PlateSouth American Plate

Tectonic plates (Let’s Talk scientific research using picture by Map:USGSDescription:Scott Nash via Wikimedia Commons).


There room eight other smaller secondary plates as well as plenty of other microplates which execute not make up far-ranging amounts the landmass. Tectonic plates no only move land masses (continental crust), but likewise oceans (ocean crust). Since the plates are floating on liquid rock, they are constantly moving and bumping versus each other. This method that the sizes and also positions of these plates readjust over time.

Tectonic plates room able to move because the lithosphere, which provides up the plates, has a higher strength and also lower thickness than the underlying asthenosphere. The heavy plates over move follow me on the fluid rock below. You may imagine the these plates space zipping along, however in fact, they space moving really SLOWLY! The speed of the plates arrays from a typical 10–40 mm/year (about as rapid as fingernails grow) come as fast as 160 mm/year (about as quick as hair grows). Geologists came to accept the concept of key Tectonics in the so late 1950s and also early 1960s after comes to know the principle of seafloor spreading. Seafloor dispersing occurs on the seafloor where oceanic plates are relocating away native each various other (diverging). When this happens, cracks happen in the lithosphere, i beg your pardon allows magma (hot fluid rock) come rise and also cool, forming a new seafloor. The opposite of divergence is convergence. This occurs as soon as plates are moving towards every other. Material may press upwards (obduction) creating mountains or downwards (subduction) into the mantle. The material shed through subduction is approximately balanced by the formation of brand-new (oceanic) tardy by seafloor spreading.

Volcanic eruptions and earthquakes can take place and mountains and ocean trenches can be formed when tectonic plates meet. Let’s look at several of these processes in much more detail.

Mountains and Volcanoes

What perform mountains and volcanoes have actually in common? They are both large, steep terrain made that rock that are created when tectonic plates room pushed and pulled. Even if it is you get mountains or volcanoes depends on the type of tectonic plates and where they are colliding.

To know whether friend will obtain mountains or volcanoes, you should remember two things.

There are two significant types that tectonic plates: oceanic and continental.Oceanic plates space denser than continental plates.

Let’s look at exactly how tectonic plates form mountains and volcanoes.

When two oceanic plates diverge (pull apart), undersea volcanoes are formed. Volcanoes are resulted in by crack in the earth crust. An instance of this is the Mid-Atlantic Ridge, i beg your pardon extends native the Arctic s to past the southern tip of Africa. There room so numerous volcanoes in the Mid-Atlantic Ridge, and they space so large, the it is taken into consideration the longest mountain variety in the world. Iceland is located on this ridge. The red triangle on the picture show where there are energetic volcanoes.When an oceanic bowl (1) converges with a continental plate (2), the oceanic key will relocate under the continent plate (subduction) because it is denser (3). The oceanic plate may go deep sufficient under the continent plate and into the mantle the it melts and also forms magma (4). Enhanced pressure from beneath the earth can build up and cause the magma to seep up v weak clues in the crust (5). Magma under high pressure periodically comes v volcanic vents in the kind of flowing lava, creating a volcanic cone (6).

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Subduction of an oceanic bowl (Let’s Talk science using a publicly domain photo on Wikimedia Commons).