Major Plates of the Lithosphere: Earth’s Tectonic Plates
The outer shell of the earth, the lithosphere, is broken up into tectonic plates. The seven major plates are the African plate, Antarctic plate, Eurasian plate, Indo-Australian plate, North American plate, Pacific plate and South American plate.
Planet Earth
You are certainly familiar with the pictures of planet Earth showing its large land masses separated by brilliant blue oceans. In fact, if you were given a multiple-choice quiz right now, I bet you’d be able to identify the major land masses based on their shapes and locations. If you are from America, you might start by labeling North America and South America.
From there, you would probably be able to identify the big land mass to the east as Africa and the land mass that it wears as a hat as Europe. From Europe, it’s a short trip east to Asia, which snuggles up to India at its base. The big continent at the bottom of the globe is easily recognized as Antarctica, and by process of elimination, you would label the remaining area as Australia.
But is this always the way planet Earth has looked? According to geologists, at one time, these major land masses were all bunched together as one big supercontinent. This supercontinent then broke apart, and over time, the continents drifted into their current locations.
Plate Tectonics
How this drifting apart of major land masses occurred was a mystery for many years and highly debated among scientists. But when the theory of plate tectonics was introduced, much of the debating quieted down. Plate tectonics is the theory that Earth’s crust is broken up into plates.
It is as if the planet’s surface is cracked, much like the cracks that would form on the outside of a hardboiled egg if you were to drop it. These large cracks in the earth’s surface form plate-like sections of Earth’s crust referred to as tectonic plates.
These plates are actually pieces of the planet’s lithosphere, which is the outermost shell of the earth made up of the earth’s crust and upper part of the mantle, and for this reason, tectonic plates are sometimes called ‘lithospheric plates.’ These plates float on top of the hotter and more fluid asthenosphere, which is the layer below the lithosphere. There are seven major tectonic plates that very slowly move around on the surface of our planet along with a number of minor plates. Let’s take a look at the seven major plates of the lithosphere.
North American and South American Plates
At the start of this lesson, we identified some major land masses found on Earth. This gets us closer to understanding the location of the major tectonic plates, but it doesn’t share the whole story. This is because tectonic plates can contain both continental crust and oceanic crust. Therefore, some of the plates may contain land, but others may be located underwater or be a mix of both.
Take the North American plate for example. It is one of the major plates of the lithosphere and extends from the middle of the Atlantic Ocean to the West Coast of North America. The same can be said for the South American plate, which is another of the seven major plates and extends from the middle of the Atlantic Ocean to the west coast of South America.
Pacific Plate
So, you can see below that the North and South American plates contain oceanic crust, even though they are named for the main continent they encompass. In fact, six of the seven major tectonic plates are named after the continents they contain. The one exception is the Pacific plate, which lies beneath the Pacific Ocean. Not only is this the only major tectonic plate that is mainly underwater, it is also the largest, spanning over 100 million square kilometers.
The majority of plates are named after the continents they contain.
pacific plate diagram
African Plate and Eurasian Plate
Tectonic plates border each other.
tectonic plate borders
Now, you might be noticing above that these major tectonic plates bump up against each other. When tectonic plates meet, they become a site for tectonic activity. Depending on whether the plates are moving toward each other, sliding past each other or pulling apart, tectonic activity might include mountain building, earthquakes, tremors or volcanoes.
In the southern Atlantic Ocean, we see below that the South American plate meets the African plate, which is the major plate that includes Africa and surrounding oceanic crust. They meet at the Mid-Atlantic Ridge, which is a large underwater mountain range on the floor of the Atlantic Ocean caused by diverging tectonic plates.
The African plate is the major plate that includes Africa.
african plate
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