Contents
- What is a tectonic plate?
- How many tectonic plates are there on Earth?
- microplates
Earthquakes, volcanoes and mountains, the most destructive events on our planet, are the result of tectonic activity. This tectonic activity is also caused by tectonic plates. So, what are these tectonic plates and how many tectonic plates are there?
What is a tectonic plate?
The earth has layers, just like an onion. Tectonic plates consist of the outermost layer, a thin layer of rock known as the crust, and part of the semi-molten upper mantle, together called the lithosphere. It “floats” above the asthenosphere, a weaker and more viscous layer of rock, allowing the plates to move.
When the world first formed, these plates did not yet exist. Our planet was a much hotter place billions of years ago, beginning its life as a searingly hot ball of liquid rock. Then, the Earth slowly began to cool, solidify and form the lithosphere. Researchers think it started breaking apart into plates about three to four billion years ago, but opinions differ on how long it took. A study earlier this year suggested this could be a billion-year process.
How many tectonic plates are there on Earth?
The answer to the total number of tectonic plates depends on who you ask in the field of geology. Scientists seem to agree that there are seven main plates. The largest of these, the Pacific Plate, has a huge area of 103 million square kilometers.
The issue of how many small plates there are is a little more controversial. It is generally accepted that there are at least five smaller plates. “In addition to the seven very large plates, there are five slightly smaller plates: the Philippine Sea, Cocos, Nazca, Arabian and Juan de Fuca,” geophysicist Saskia Goes of Imperial College London said in an interview with LiveScience.
But some geologists argue there is more. For example, The Geological Society; Scotia notes that there are eight smaller plates, adding the Caribbean and Indian plates. This brings the total number of tectonic plates to 15.
microplates
However, there are also microplates. These are literally “breakaways from the old block” that form at main plate boundaries but move independently of the plate from which they broke away. Microplates are not usually included in maps and their sizes are not clearly defined, so it is difficult to know how many there are.
“The number of microplates will continue to change as we learn more about how different scientists choose to define them and how and where deformation at plate boundaries is localized,” Goes said.
So if scientists choose to include these in the total number of tectonic plates, then that number will likely continue to change as well…
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