March 7, 2021

When the earth lost its mountains

Snowy mountains in Colorado (United States).

Snowy mountains in Colorado (United States).

The tectonic processes that form the mountains stagnated during the Proterozoic, leaving the continents devoid of high mountains for nearly 1 billion years.

Since mountain building is crucial to nutrient cycling, the prolonged change in the activity of the earth’s crust may have led to the “1 billion years of boredom”, an eon in which the evolution of life on Earth stopped, according to a new study by researchers from China, Canada and the United States published in ‘Science‘.

On geological timescales, even mountains are ephemeral. The enormous tectonic forces that propel vast swaths of the planet skyward are countered by the endless erosion processes. Since the thickness of the Earth’s crust is constantly changing, tracking the formation of mountains over time is challenging, but crucial to understanding the evolution of the planet’s surface and the life that lives on it.

The Peking University Researcher Ming Tang and his colleagues have presented a new indicator for understanding mountain-building (orogenic) processes.

Using europium anomalies in long-eroded zircons of ancient landforms to estimate the mean crust thickness throughout Earth’s history, Tang and his team discovered that mountain formation stopped for nearly a billion years during Earth’s Middle Ages.

While the continental crust was thick and active during the Archaic and Phanerozoic eons, the Proterozoic witnessed little activity, resulting in a steady decrease in the thickness of the crust as the mountains slowly eroded.

The authors suggest that this orogenic inactivity could be related to the supercontinent Nuna-Rodina, which could have altered the thermal structure of the mantle, weakening the activity of the continental crust above. With no new nutrients reaching the planet’s surface, the changes could also have caused persistent famine in the oceans and thus halted the evolution of life for a time.


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