A boring billion for mountains
Earth's crust has changed over time as supercontinents formed and broke apart. Tied into this cycle are the building and erosion of high mountains, which are tied to collisions between tectonic plates. Tang et al. use europium anomalies in zircons to estimate the mean thickness of crust over Earth's history. This proxy shows that mountain building has not always been as active as it is today or as it was very early in Earth's history. Mountain building, and the subsequent erosion, was less intense for about a billion years, roughly correlated with a so-called “boring billion” period of biological evolution.
Science, this issue p. 728
Abstract
Mountain belts modulate denudation flux and hydrologic processes and are thus fundamental to nutrient cycling on Earth’s surface. We used europium anomalies in detrital zircons to track mountain-building processes over Earth’s history. We show that the average thickness of active continental crust varied on billion-year time scales, with the thickest crust formed in the Archean and Phanerozoic. By contrast, the Proterozoic witnessed continuously decreasing crustal thickness, leaving the continents devoid of high mountains until the end of the eon. We link this gradually diminished orogenesis to the long-lived Nuna-Rodinia supercontinent, which altered the mantle thermal structure and weakened the continental lithosphere. This prolonged orogenic quiescence may have resulted in a persistent famine in the oceans and stalled life’s evolution in Earth’s middle age.
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February 12, 2021 at 01:59AM
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Orogenic quiescence in Earth's middle age - Science Magazine
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