The formation of continental crust plays a central role in stabilizing the climate and creating unique environments for life. It is associated with plate tectonics and may constrain the timing and mechanisms of solid Earth differentiation. However, the growth history of continental crust is highly controversial, ranging from rapid extraction shortly after Earth’s formation to late gradual growth after ~3.8 billion years ago.

More than half of Earth’s continental crust was produced during the beginning of the Archaic geologic age, 4 billion years ago, when crust formation was previously believed to have begun, according to a new study.

Guo, a graduate student in Yale’s Department of Earth and Planetary Sciences and first author of the study, said: “If we want to make a cake or cookies from scratch, we have to mix flour, sugar, eggs, butter, etc. in a bowl and it takes time to mix all the ingredients into a smooth dough.”

Guo of Yale University said: “The Earth’s mantle convects like boiling water in a pan, and this convection mixes different components in the mantle formed by the formation of continental crust.”

The scientists created a new theoretical model that analyzed signs of the chemical elements hafnium and neodymium in the Earth’s mantle, which have long been used to understand the history of continental crust.

According to the researchers, because of the time it takes for convection to mix, certain hafnium and neodymium marks occurring during the Archean eon should have formed much earlier during the Hadean.

The new modeling approach not only accounted for a longer mixing process, but also approximated its time frame. This shows that the continental crust formed much earlier than previously thought.

Korenaga, a professor of earth and planetary sciences at the Yale Faculty of Arts and Sciences, said: “Incorporating this physical common sense into a geochemical analysis requires a very extensive modeling effort, which has been a challenging task for geochemists for decades.”

He also said, “The formation of continental crust is a crucial factor in stabilizing the climate and creating unique environments for life to emerge and evolve. Our research sheds new light on this important process.”

The result shows that the mass balance with continental crust determines the formation and recycling of the Earth’s crust.

Magazine reference:

  1. Meng Guo et al. The combined Hf and Nd isotope evolution of the depleted mantle requires Hadean continental formation. Scientific progress. DOI: 10.1126/sciadv.ade2711