The Tectonic plates move Because they are floating on the liquid mantle of the earth. This mantle in turn also moves due to the convection currents that cause the hot rock to rise, give off some heat and then fall.
This phenomenon of the liquid mantle generates eddies of liquid rock below the earth's crust, which are transferred to the plates (BBC, 2011).
Map of tectonic plates.
Tectonic plates are underground layers that move, float and sometimes fracture, and whose movement and shock can trigger phenomena of continental drift, earthquakes, volcanoes, formation of mountains and oceanic trenches.
The depth of the liquid mantle makes it difficult to study, so it has not yet been possible to determine completely the nature of its behavior. However, it is believed that tectonic plate motions are caused in response to sudden stresses and not due to underlying temperature changes.
The process of forming plate tectonics or plate tectonics can take hundreds of billions of years to take place. This process does not occur uniformly, since small pieces of plaque can join with each other, generating earth surface jolts that vary in intensity and duration (Briney, 2016).
Apart from the convection process there is another variable that causes the plates to move and is gravity. This force causes the tectonic plates to move a few centimeters each year, making the plates have distanced themselves enormously from each other over the course of millions of years (EOS, 2017).
Convection currents
The mantle is a liquid material but dense enough for the tectonic plates to float on it. Many geologists think that the reason the command flows is because it gives rise to a phenomenon known as convection currents that has the ability to move the tectonic layers (Engel, 2012).
Convection currents are generated when the hottest part of the mantle rises, cools and submerges. Repeating this process several times generate the movement necessary to move the tectonic plates, which have freedom of movement depending on the force with which convection currents rotate the mantle.
The linear motion of the plates can be explained by the way the convection process forms units of fluid mass or cells which in turn move in different directions as seen in the following graph:
The convection cells are constantly changing and behave within the parameters of a chaotic system, which allows the generation of different unpredictable geographical phenomena.
Some scholars compare this phenomenon with the movement of a child playing in a bathtub full of toys. In this way the land surface can be united and separated several times in an indeterminate period of time (Jaeger, 2003).
Subduction process
If a plate located under the oceanic lithosphere meets another plate, the dense oceanic lithosphere is submerged under the other plate sinking into the mantle: this phenomenon is known as a subduction process (USGS, 2014).
As if it were a tablecloth, the sinking oceanic lithosphere drags the rest of the tectonic plate, causing its movement and a violent jolt in the earth's crust.
This process causes the separation of the oceanic lithosphere in several directions, giving rise to oceanic baskets, where a new, warm and light oceanic crust can be created.
The subduction zones are places where the earth's lithosphere sinks. These zones exist in the converging zones of the plate boundaries, where a plate of oceanic lithosphere converges with another plate.
During this process there is a plaque that descends and another that overlies the descending plate. This process causes one of the plates to tilt at an angle between 25 and 40 degrees to the Earth's surface.
Continental drift
The theory of continental drift explains how the continents changed their position on the earth's surface.
This theory was raised in 1912 by Alfred Wegener, a geophysicist and meteorologist who explained the phenomenon of continental drift based on the similarity of fossils of animals, plants and various rock formations found on different continents (Yount, 2009).
It is believed that the continents were once united in the manner of Pangea (a continent of more than 300 million years old) and subsequently separated and displaced the positions we are currently familiar with.
These displacements were caused by the movements of the tectonic plates that took place during millions of years.
The curious thing about the theory of continental drift is that it was initially discarded and endorsed decades later with the help of new discoveries and technological advances in the field of geology.
Speed of movement
Nowadays it is possible to trace the speed of movement of the tectonic plates thanks to the magnetic bands located in the bottom of the ocean floor.
They can record variations in the Earth's magnetic field, allowing scientists to calculate the average speed at which the plates separate. Such speed can vary greatly depending on the plate.
The plate located in the Cordillera del Arte has the slowest speed rate (less than 2.5 cm / year), while the eastern Pacific plateau near Easter Island in the South Pacific, 3,400 km west Of Chile, has the fastest movement rate (more than 15 cm / year).
The speed of movement can also be obtained from the geological mapping studies that allow to know the age of the rocks, their composition and structure.
These data allow us to identify if one plate boundary coincides with another and the rock formations are the same. By measuring the distance between the formations, an estimate can be given of the speed with which the plates have moved in a given period of time.
References
- (2011). BBC. Retrieved from Changes to the Earth and its atmosphere: bbc.co.uk.
- Briney, A. (2016). About Education. Retrieved from Plate Tectonics: geography.about.com.
- Engel, J. (2012, 37). Quora . Retrieved from Why of tectonic plates move?: quora.com.
- (2017). Earth Observatory of Singapore. Retrieved from Why of tectonic plates move?: earthobservatory.sg.
- Jaeger, P. (Director). (2003). Causes of Tectonic Plate Movement [Motion Picture].
- (2014, 1995). U.S. Geological Survey . Retrieved from Understanding plate motions: usgs.gov.
- Yount, L. (2009). Alfred Wegener: Creator of the Continental Drift Theory. New York: Chelsea House Publishers.