Here's a breakdown:

* Continental crust: Typically ranges from 30 to 70 kilometers (19 to 43 miles) thick. It's made up of less dense, granitic rocks.

* Oceanic crust: Much thinner, ranging from 5 to 10 kilometers (3 to 6 miles) thick. It's composed of denser, basaltic rocks.

This difference in thickness and composition is why continents rise above the ocean floor.