Earth's crustal evolution involves the formation, destruction and renewal of the rocky outer shell at that planet's surface. The variation in composition within the Earth's crust is much greater than that of other terrestrial planets. Mars, Venus, Mercury and other planetary bodies have relatively quasi-uniform crusts unlike that of the Earth which contains both oceanic and continental plates. This unique property reflects the complex series of crustal processes that have taken place throughout the planet's history, including the ongoing process of plate tectonics. The proposed mechanisms regarding Earth's crustal evolution take a theory-orientated approach. Fragmentary geologic evidence and observations provide the basis for hypothetical solutions to problems relating to the early Earth system. Therefore, a combination of these theories creates both a framework of current understanding and also a platform for future study. Early crust Mechanisms of early crust formation The early Earth was entirely molten. This was due to high temperatures created and maintained by the following processes: Compression of the early atmosphere Rapid axial rotation Regular impacts with neighbouring planetesimals. The mantle remained hotter than modern day temperatures throughout the Archean. Over time the Earth began to cool as planetary accretion slowed and heat stored within the magma ocean was lost to space through radiation. A theory for the initiation of magma solidification states that once cool enough, the cooler base of the magma ocean would begin to crystallise first. This is because pressure of 25 GPa at the surface cause the solidus to lower. The formation of a thin 'chill-crust' at the extreme surface would provide thermal insulation to the shallow sub surface, keeping it warm enough to maintain the mechanism of crystallisation from the deep magma ocean. The composition of the crystals produced during the crystallisation of the magma ocean varied with depth. Experiments involving the melting of peridotite magma show that deep in the ocean (>≈700 m), the main mineral present would be Mg-perovskite, whereas olivine would dominate in the shallower areas along with its high pressure polymorphs e.g. garnet and majorite. A contributing theory to the formation of the first continental crust is through intrusive plutonic magmatism. The product of these eruptions formed a hot, thick lithosphere which underwent regular cycling with the mantle. The heat released by this form of volcanism, as well as assisting mantle convection, increased the geothermal gradient of the early crust. Crustal dichotomy The crustal dichotomy is the distinct