How is a pizza like Earth's crust?

Pizza crust =  Mantle
Sauce = Asthenosphere
Cheese = Oceanic crust
Toppings = Continental crust

The mantle is made of iron and silicate materials and everything else on earth is on top of it. The asthenosphere is the top layer of the mantle. The Oceanic crust is more dense than continental crust, so the toppings go on top of the cheese.