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Archean subduction
Archean subduction is a contentious topic involving the possible existence and nature of subduction in the Archean, a geologic eon extending from 4.0-2.5 billion years ago. Until recently there was little evidence unequivocally supporting one side over the other, and in the past many scientists either believed in shallow subduction or its complete non-existence. However, the past decade has witnessed the potential beginning of a change in geologic understanding as new evidence is increasingly indicative of episodic, non-shallow subduction.
==The importance of Archean subduction==
Subduction is the density-driven process by which one tectonic plate moves under another and sinks into the mantle at a convergent boundary. Gravitational pull from dense slabs provides approximately 90% of the driving force for plate tectonics, and consequently subduction is crucial in changing the Earth's layout, guiding its thermal evolution and building its compositional structure.〔 In particular, subduction zones are the primary sites of present-day continental crust formation, another process of modern Earth that has a mysterious past. Furthermore, subduction is the main mechanism by which surface materials enter the deep Earth and is also largely responsible for the formation of ores. Considering the importance of subduction in many geological processes, it is clear that studying its past and present nature is essential to developing our understanding of the Earth as a dynamic system.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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