Explain how the movement of tectonic plates at convergent, divergent, and transform boundaries creates Earth's major landforms.
Earth's outer shell, the lithosphere, is not one solid piece -- it is cracked into roughly a dozen major tectonic plates that float on the slowly flowing, softer rock layer beneath them and drift just a few centimeters a year, about as fast as your fingernails grow. That tiny, relentless motion has built every mountain range, ocean trench, and earthquake zone on the planet over millions of years.
Where two plates collide (a convergent boundary), the crust crumples upward into mountains, or one plate dives beneath the other (subduction), often producing volcanoes and deep ocean trenches. Where two plates pull apart (a divergent boundary), magma rises to fill the gap, building new crust -- most of this happens unseen along mid-ocean ridges, though East Africa's Great Rift Valley shows the process on land. Where two plates grind sideways past each other (a transform boundary), no new land is built or destroyed, but the friction produces powerful earthquakes -- California's San Andreas Fault is the textbook example.
Mastery looks like: They can name the three plate boundary types, describe the landform or hazard each produces, and explain a real example in terms of plate motion.
Common stumbles: Confusing divergent (pulling apart, building new crust) with convergent (colliding, crumpling or subducting); assuming all convergent boundaries produce volcanoes, when continent-continent collisions instead fold into mountains.