How Tectonic Plates Move
Understand that convection currents in the molten mantle drive the movement of rigid tectonic plates; distinguish between convergent (collision/subduction), divergent (spreading ridges), and transform (sliding) plate boundaries; explain why volcanoes, earthquakes, and mountain chains cluster at boundaries; introduce the Wilson cycle of supercontinent assembly and breakup
The lesson
You already know Earth has layers, and that heat keeps moving inside the mantle. That movement is called a convection current: hot rock rises, cools, and sinks back down in a slow loop. These currents drag the rigid plates riding on top of the mantle, which is why the plates never stop moving, even though you cannot feel it.
Where two plates meet, they move in one of three ways. At a divergent boundary, like the Mid-Atlantic Ridge, plates pull apart and new crust rises to fill the gap. At a convergent boundary, plates crash together, and one often slides under the other. At a transform boundary, like the San Andreas Fault, plates grind past each other sideways without creating or destroying crust.
Where the Nazca Plate meets the South American Plate, the thinner ocean plate is forced underneath the thicker continental plate. This sinking process is called subduction, and it happens at a convergent boundary. It explains why the Andes Mountains keep rising, why earthquakes shake the region, and why volcanoes erupt there: the sinking plate melts deep underground, and the melted rock pushes back up.
Volcanoes, earthquakes, and mountain ranges are not scattered randomly across the globe. They trace the edges of the plates, forming patterns like the Pacific Ring of Fire. A pattern on a hazard map is really a map of plate boundaries.
Mantle convection drives plates together, apart, or past each other at convergent, divergent, and transform boundaries, which is why quakes, volcanoes, and mountains trace patterns like the Ring of Fire.
Watch it
Where it sits
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Where this leads
Jobs that lean on this skill. Follow one to see everything it is built on.
8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.