Earth’s crust is made up of a dozen or so major lithospheric plates. The other name for lithospheric plates is crustal plates.
So there’s about a dozen of these and these crustal plates float upon the earth’s mantle. So another name for earth’s mantle is this really big word, this hard to wrap your tongue around called the Asthenosphere.
The transcript is for your convenience.
These plates move about each other in response to complex convection currents, set in motion by earth’s interior heat. The earth’s interior heat sets in motion complex convection currents which then move the plates around.
Now, divergent boundaries are the places where two plates move apart from each other. Another name for a divergent boundary is a spreading center. These spreading centers or divergent boundaries are where two plates move apart from each other. The opposite of that is a conversion boundary. As you probably already guessed, that’s where two plates come together.
You may be thinking about an earthquake which usually what comes mind when people think about plates. Earthquakes happen when left and right lateral strike slip movement between plates occurs during transform faults. So it’s a left and right lateral strike slip movement that’s going on here forming that earthquake.
Now sometimes oceanic crust collides with the continental crust. Oceanic crust is thin and dense whereas continental crust is thick and light. So what happens is the oceanic crust subducts beneath the continental crust. The subducted material carries scraped-off continental crust and seawater down with it. Now, all that material is going to melt because of the intense heat. So as this material melts, it rises as a mixture of magma and steam which produces explosive volcanic mountain ranges like those ringing in this Pacific Ocean basin. That’s how volcanic actions occurs. So that’s a look at plate tectonics.