Here's a breakdown:

* Oceanic crust:

* Typically ranges from 5 to 10 kilometers (3 to 6 miles) thick.

* Composed primarily of basalt and gabbro, which are denser than the rocks that make up continental crust.

* Younger than continental crust, as it is constantly being created at mid-ocean ridges and destroyed at subduction zones.

* Continental crust:

* Ranges from 30 to 70 kilometers (19 to 43 miles) thick.

* Made up of a variety of rocks, including granite, metamorphic rocks, and sedimentary rocks.

* Much older than oceanic crust, with some continental rocks dating back billions of years.

The difference in thickness and density explains why oceanic crust is often subducted beneath continental crust at convergent plate boundaries.