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Formation of Earth's Crust

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Science  28 Jul 2000:
Vol. 289, Issue 5479, pp. 511
DOI: 10.1126/science.289.5479.511b

A mystery in the evolution of Earth's surface is the origin and timing of growth of the continental crust. It is generally accepted that the majority of the continental crust formed within the first 2 to 3 billion years of Earth's history. The two proposed modes of growth are (i) rapid formation of the crust soon after Earth formed followed by steady-state recycling or (ii) gradual growth of the crust over 2 to 3 billion years with episodes of punctuated growth and minimal recycling. A special issue in Tectonophysics focuses on this debate.

De Smet et al. use a thermal convection model to show that rapid growth of the crust occurred within the first 0.6 billion years, and supporting geochemical evidence from the Australian craton is described by Green et al. and Krapez et al. However, Condie has modeled a few periods of punctuated growth caused by episodic collapse of layered convection between 3 to 1 billion years ago (Ga), which supports the gradual growth model. Although there is no compelling resolution of this debate, Abbott et al. provide a useful inventory of the amount of continental crust that may have formed early in Earth's history; they estimate that 29 to 45% of the total volume of continental crust was formed by 2.7 Ga and 51 to 79% was formed by 1.8 Ga. — LR

Tectonophysics322, 19; 69; 89; 153; 163 (2000).

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