Continents and oceans are both fragments of the same thermal structure. They both have an upper firm mechanical layer wherein heat loss is by conduction and a lower thermal boundary layer where convection is prevailing. However, continental crust is typically granite, a coarse-grained igneous rock, whilst oceanic crust is mostly basalt, a fine-grained igneous rock. Granite is rich in minerals that have silica and aluminum, on the other hand, basalt is rich in minerals that have iron and magnesium. Continental crust is less dense and thicker compared to oceanic crust.
