Continent Formation

Model Ideas

1. Earth’s crust is broken into big chunks called plates.
2. Plates can be moving away from each other (diverging), toward each other (converging), or sliding along each other (transforming).
3. New oceanic crust forms at diverging plate boundaries. As oceanic plates diverge, magma from the mantle flows up, cools, forms new oceanic crust, and fills in the gap
4. On average, oceanic crust is more dense than continental crust so when they converge the more dense plate (oceanic) subducts, or slides beneath, the less dense plate
5. Over Earth’s surface, the amount of new crust forming must be in balance with the amount of old crust being subducted back into the mantle.
6. New continental crust forms along converging boundaries where one plate subducts under another one. The action of subduction produces low-density magma which can rise to the surface and form new continental crust: volcanic islands, mountain ranges, and granite formations.
7. Once low-density rock (continental crust) forms on Earth’s surface, it can’t sink again. It is stuck on the surface because of its density.
8. The total amount of continental crust on Earth slowly increases over time.