Crustal Structure of the Earth

The boundary between the crust and the mantle was discovered by Mohorovicic in 1909 under the European continent. Subsquent research in this century established the major differences between the continental and oceanic crust; a typical thickness for the continental crust is 30-50 km while a typical thickness for me oceanic crusts is 6 km. In terms of history the continental crust contains a much longer history of 4 billion years, whereas the oceanic crust contains at most 200 million years of history because of recycling of oceanic plates. Because of its long history, the continental crust has been subjected to various tectonic processes, such as repeated episodes of partial melting, metamorphism, intrusion, faulting and folding. It is thus easier to find systematic relationships between age and structure of oceanic crusts. However, the existence of hotspots as well as changing patterns of plate motion complicate oceanic crustal structure. In this section, we assemble crustal thickness data from various tectonic provinces and discuss their implications.