2.4 Billion Years Ago, Earth's First Snow Fell as Oxygen Appeared with Rising Land

The emergence of so much land changed the flow of atmospheric gases and other chemical and physical processes, primarily between 2.4 billion and 2.2 billion years ago, he said. It also happened amid large-scale changes in mantle dynamics.

“What we speculate is that once large continents emerged, light would have been reflected back into space and that would have initiated runaway glaciation,” said Bindeman, a third-generation geologist who grew up in Russia. “Earth would have seen its first snowfall.”

Chemical changes recorded in the rocks coincide with the theorized timing of land collisions that formed Earth’s first supercontinent, Kenorland, and the planet’s first high-mountain ranges and plateaus. When the planet was much hotter, Bindeman said, such mountainous land could not be supported.

“Land rising from water changes the albedo of the planet,” he said. “Initially, Earth would have been dark blue with some white clouds when viewed from space. Early continents added to reflection.”

The rapid changes, the researchers noted, may have triggered what scientists call the Great Oxygenation Event, in which atmospheric changes brought significant amounts of free oxygen into the air.

Scientists have long believed that Earth experienced a gradual or stepwise emergence of land between 1.1 billion and 3.5 billion years ago. Bindeman’s study points to an age near the middle of that span.

The timing also coincides with the transition from the Archean Eon, when archaea and bacteria — simple, single-cell life forms — thrived in water, to the Proterozoic Eon, when more complex life forms, such as algae, plants and fungi, emerged.

UO co-authors with Bindeman, who was supported by the National Science Foundation, were doctoral student David O. Zakharov and research associate James Palandri, both in Bindeman’s UO lab, and Gregory J. Retallack, a professor in the UO Department of Earth Sciences.

Contacts and sources:
Jim Barlow
University of Oregon

Citation: Rapid emergence of subaerial landmasses and onset of a modern hydrologic cycle 2.5 billion years ago.
I. N. Bindeman, D. O. Zakharov, J. Palandri, N. D. Greber, N. Dauphas, G. J. Retallack, A. Hofmann, J. S. Lackey, A. Bekker. Nature, 2018; 557 (7706): 545 DOI: 10.1038/s41586-018-0131-1