Welcome to the world of plate tectonics, in this article you will find maps, images, and drawings about plate tectonics, its parts, operation, and importance. In addition, it is explained in detail how they are formed and how they influence the dynamics of the planet earth.
The tectonic plates or lithospheric plates can be compared to a crust or rigid superficial layer that surrounds the planet earth and that are fragmented like a puzzle forming part of the continents and ocean floors, in depth they reach up to 150 km.
Plate tectonics is the most superficial rigid layer of the planet that includes the Earth’s crust and a part of the equally rigid upper mantle.
The fragments of tectonic plates are limited by the “borders or limits of plates” that can be convergent, divergent or transforming, these fragments make up the different types of tectonic plates.
Plate tectonics is the earth’s crust fragmented?
It is often mistakenly believed that the tectonic plates are the fragmented crust, however, geologists currently know that what is actually fragmented is the lithosphere.
Therefore, the lithosphere is the layer that makes up the tectonic plates and in turn they are called lithospheric plates and not the crust as is often wrongly assumed.
Parts of a tectonic plate
Now that we know that a tectonic plate is not the same as the crust, we must understand what its parts are or what it is made of.
A tectonic plate clearly includes the lithosphere, the lithosphere is made up of the crust and a part of the rigid upper mantle.
Therefore, a tectonic plate would be equal to the lithosphere and the lithosphere is equal to the crust plus the rigid upper mantle, sounds like a mathematical sum.
Now, a lithosphere plate can be oceanic and continental, but that is the subject of another article that by the way click here.
Now, the tectonic plates “move” some expand, others contract, but for this they must float on another layer that has a plastic behavior that allows this movement and in reality it is so, the lithosphere is floating on the asthenosphere.
Characteristics and properties
The nature of a tectonic plate can be summarized as follows:
- A plate is a segment of the lithosphere; therefore, it includes the upper mantle and all of the overlying Earth’s crust.
- A single plate can carry both oceanic crust and continental crust. The average thickness of a lithospheric plate covered by oceanic crust is 75 kilometers, while that of the lithosphere covered by a continent is 125 kilometers. The lithosphere can be as little as 10 to 15 kilometers thick at an oceanic spreading center.
- A plate is composed of hard, mechanically strong rock.
- A tectonic plate floats on top of the underlying hot plastic asthenosphere and slides horizontally on it.
- A tectonic plate behaves like a slab of ice floating in a pond. It can flex slightly, as thin ice does when a skater passes by, allowing for minor vertical movements. In general, however, each plate moves like a large, intact sheet of rock.
- A plate margin is tectonically active. Earthquakes, mountain ranges, and volcanoes are common at plate boundaries. In contrast, the interior of a lithospheric plate is normally tectonically stable.
- Tectonic plates move at speeds that vary from less than 1 to 16 centimeters per year. Because the continents and oceans form the tops of the moving lithosphere, both the continents and the oceans migrate across the Earth’s surface at the same rate that the plates move.
Major tectonic plates
The lithosphere is made up of about two dozen segments that have irregular sizes and shapes called lithospheric plates or tectonic plates that are in constant motion relative to each other.
Seven major lithospheric plates are recognized. These plates, which make up 94 percent of Earth’s surface, include the North American, South American, Pacific, African, Eurasian, Australian-Indian, and Antarctic plates.
The largest is the Pacific plate, which spans a significant portion of the Pacific Ocean basin.
The other six large plates include an entire continent plus a significant amount of ocean floor.
The South American plate spans almost all of South America and about half of the South Atlantic floor.
Also note that neither plate is completely defined by the margins of a single continent.
Minor tectonic plates
Intermediate-sized plates include the Caribbean, Nazca, Philippine, Arabian, Cocos, Scottish, and Juan de Fuca plates. These plates, with the exception of the Arabian plate, are composed primarily of oceanic lithosphere.
In addition, there are several smaller plates (microplates), but these cannot be shown on the map due to their scale.
Why tectonic plates move?
After geologists developed the theory of plate tectonics, they began to wonder, why do large slabs of lithosphere slide across the Earth’s surface?
Recent research shows that after subduction begins, a tectonic plate sinks to the core-mantle boundary, to a depth of 2,900 kilometers.
At the same time, equal volumes of hot rock rise from the deep mantle to the surface below a spreading core, forming new lithosphere to replace the loss through subduction.
The term convection refers to the up and down flow of fluid material in response to heating and cooling.
The process of mantle convection continuously stirs the entire mantle as rock that is hotter than its surroundings rises toward Earth’s surface and old plates that are cooler than their surroundings sink into the mantle.
A single mantle convection cell can be thousands of kilometers in diameter. In this way, the entire mantle-lithosphere system circulates in large cells, transporting rocks from the central mantle boundary to the Earth’s surface and then back into the deeper mantle.
A pot of soup on a hot stove illustrates the convection process. The increase in temperature causes most materials, including soup (or rock) to expand.