Plate Tectonics

Earth's outer shell isn't one solid piece — it's broken into about 15 LARGE PLATES (and many smaller ones) that float on the hot, slowly-flowing mantle below. They MOVE — slowly (2-10 cm per year), but enough over millions of years to tear continents apart, build mountains, open oceans. Plate tectonics is the unifying theory of geology — explains earthquakes, volcanoes, mountain ranges, and continent shapes.

Three types of plate boundaries. CONVERGENT: plates collide. One sinks (ocean plate under continental — creates volcanoes like Andes), or both pile up (continent-continent — creates mountains like Himalayas). DIVERGENT: plates pull apart. New ocean floor forms — like the Mid-Atlantic Ridge. TRANSFORM: plates slide past each other sideways. Big earthquakes — like California's San Andreas Fault.

Pangaea. About 200-300 million years ago, all continents were joined in a supercontinent called PANGAEA. They slowly broke apart and drifted into today's positions. Africa and South America still fit like puzzle pieces (look at a map!). Continents move so slowly we don't feel it — but on geological time, the map of Earth is constantly changing.

Plate tectonics is the engine that built every mountain you can see. The map of Earth's past — and future — is in constant motion. We're lucky to live on such a dynamic planet.