GEOLOGY

Detailed explanation-1: -Continental crust is typically 40 km (25 miles) thick, while oceanic crust is much thinner, averaging about 6 km (4 miles) in thickness. The effect of the different densities of lithospheric rock can be seen in the different average elevations of continental and oceanic crust.

Detailed explanation-2: -The Earth is covered by two kinds of crust-continental and oceanic. The thinner oceanic crust is normally a little more than four miles thick, while the thicker continental crust is often as much as 25 miles thick. Continental crust is also much less dense than its oceanic counterpart.

Detailed explanation-3: -Oceanic crust differs from continental crust in several ways: it is thinner, denser, younger, and of different chemical composition. Like continental crust, however, oceanic crust is destroyed in subduction zones. The lavas are generally of two types: pillow lavas and sheet flows.

Detailed explanation-4: -The continental crust of our planet has an average chemical composition that is approximately granitic. Granite is the ultimate magmatic silicate rock and among the most prominent constituents of the upper crust.

Detailed explanation-5: -As long as subduction occurs, water is released and is delivered to the base of the crust, melting pre-existing basaltic rock to form granite magma. As it rises and cools, the granite magma crystallises to continental crust.