Perhaps you are wondering: “What is the Theory of Plate Tectonics?” Get ready to find out! This post guides you through the theory of plate tectonics and how tectonic plates move. You will learn what tectonic plates are, why they move, and what it takes for a concept to become a scientific theory. The post ends with links to a few additional tools for teaching plate tectonics, including other helpful blog posts and other related resources for studying plate tectonics and similar topics.
For Teachers: If you’re an educator planning to teach plate tectonics, you know that engaging activities and thoughtfully crafted visuals are key to deepening understanding. That’s why I create Earth science units that are packed with hands-on activities and my watercolor artwork incorporated into diagrams. The information in this post comes from my comprehensive Plate Tectonics Unit, which includes handouts, worksheets, activities, and diagrams covering tectonic plate boundaries, Earth’s layers, volcanoes, and earthquakes. I think you and your students will love it (plus you’ll support my blog with your purchase! ❤️)
What is a tectonic plate?
You may already know that the Earth is made of several compositional layers: crust, mantle, and core. You may wonder: “Why does the Earth have layers?” It all comes down to density. Density tells us about how heavy something is relative to its volume. You may have noticed that differences in density allow oil to float on top of water. The oil stays on top because it is less dense than the water. Just like oil on water, Earth’s inner materials are separated into layers based on their densities. The less dense surface “floats” on top of the denser, inner layers.
This “floating” surface, however, is not just one big piece. Earth’s lithosphere (surface; comprised of the crust and upper mantle) is cool, rigid, and brittle compared to the hotter, softer layers beneath it. The brittle lithosphere is broken into massive, irregularly shaped pieces, called tectonic plates. Picture the Earth as a hard-boiled egg with a cracked shell. Some of the tectonic plates are so large that they span entire continents. Others are smaller. Tectonic plates in the lithosphere sit atop a denser, soft part of the mantle called the asthenosphere.
Why do plates move?
Heat is the force driving plate movement. The Earth is cool on the surface but hot deep inside. Deep within the Earth, material heats and expands, causing it to rise towards the surface. As material rises, it cools and contracts, causing it to sink again. This cycle of rising and sinking creates convection currents in the mantle. These currents move the overlying tectonic plates. Of course, all this movement is happening gradually over a very long time. It is hard to imagine rocks moving and flowing, because it happens so slowly that we cannot see it. Most tectonic plates only travel a few inches or less each year.
What is the theory of plate tectonics?
The theory of plate tectonics is a scientific theory central to the field of geology. This theory explains that the surface of the Earth is broken into large plates that are slowly moving. These plates slide past and over one another. Their motion gradually changes the appearance of Earth’s landmasses and oceans over time. Plate movement also causes earthquakes and volcanic eruptions along plate boundaries.
There are a few different plate boundary types. They are:
- Convergent boundaries – plates moving together
- Divergent boundaries – plates moving apart
- Transform boundaries – plates sliding past one another
You can read more about these in my post on tectonic plate boundary types.
What is a theory in science?
Conversationally, the word “theory” can mean a hunch or guess. But in science, theory has a different meaning. A scientific theory is an explanation of events in the natural world that has been widely and repeatedly tested. Theories are universally or nearly universally accepted among scientists. This is because theories are supported by lots of evidence, gathered using the scientific method.
If new evidence is found that does not fit with a theory, the theory can be modified or rejected. A theory provides a framework that ties together and explains many observations of the natural world. Theories not only explain what is happening, but also why or how it happens.
Classroom Activity: Can you think of any other theories from science? In small groups, assign students different theories from various scientific fields. Have each group look up the theory, then explain the theory to the class in a few sentences. (Suggestions: cell theory, theory of evolution by natural selection, big bang theory, climate change, plate tectonics)
More Tools for Teaching Plate Tectonics
If you want to continue learning more about plate tectonics, try one of these:
- Read about tectonic plate boundary types in my blog
- Read about the compositional and mechanical layers of the Earth in my blog
- Build your own layers of the Earth model
- Try some of these 8 plate tectonics learning activity ideas
- Read about the types of volcanoes
- Teach plate tectonics with my complete Plate Tectonics Unit.
Study Plate Tectonics with Wild Earth Lab!
There’s no need to scramble to put together the perfect plate tectonics lessons– I’ve already created them for you and organized them into a complete Plate Tectonics Unit! This set includes all the printable materials you need for studying tectonic plates, the layers of the Earth, volcanoes, and earthquakes.
Explore more lessons from Wild Earth Lab:
If you enjoyed this post, I know you will love trying my other printable science and nature units in your classroom too!
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