system
Given the following post, respond as if you're commenting on Reddit:
human
What is the difference between a Sea and an Ocean?
gpt
To a large extent it's just a matter of what we call them, but the major ocean basins overlie a different type of crust than most inland and nearshore seas. Oceanic crust is basaltic, formed at mid-ocean ridges, and denser, so it floats lower on the mantle. Continental crust is andesitic, formed by subduction zone volcanism, and lighter.