# Why does Earth have two kinds of crusts?

Why does Earth have two clearly differentiated kinds of crusts, namely continental and oceanic? How did they differentiate initially and why don't they get mixed up over time?

• Such a simple question, with such a hard and complicated answer. It is still one of the heavily debated topics in geology. – Gimelist Mar 27 '18 at 5:55
• I think an intrusive vs extrusive answer could be made, but as geology isn't my subject, I'd prefer that someone not be me. www2.nau.edu/~gaud/RiodeFlag/ignsrck.htm – userLTK Mar 27 '18 at 11:32