If the oceanic crust were a person, it would be a teenager—always being recycled. It’s never older than 200 million years, which is a blink in Earth’s 4.5-billion-year timeline.
Continental crust is the grumpy old grandparent that refuses to die. Some chunks are over 4 billion years old, and they’ve been floating around like immortal couch potatoes.
Fun fact: oceanic crust is constantly being created at mid-ocean ridges and destroyed in subduction zones. It’s the planet’s most dramatic conveyor belt, and yes, it’s always on a recycling rampage.
Why One Sinks and the Other Doesn’t
Oceanic crust is made of denser rock, like basalt, which contains heavy minerals like iron and magnesium. It’s basically Earth’s version of a lead weight.
Continental crust is mostly granite, which is lighter and full of quartz and feldspar. It floats higher on the mantle, which is why we have dry land and not a water world.
Ever heard of isostasy? It’s a fancy word for “stuff floats at different levels.” Continental crust is the giant marshmallow, oceanic crust is the brick—and they both have to obey gravity’s judgment.
