Oxygen Atmosphere Linked to Earth's Mantle

A new study proposes that the subduction of tectonic plates and the resulting changes in the Earth's mantle may have played a role in the increase of oxygen levels in the atmosphere. The research, led by Wei Shi of the Chengdu University of Technology, found that the timing of jumps in oxygen levels aligns with changes in the subduction of tectonic plates.

Earth's Oxygenation History

The oxygenation of Earth's atmosphere occurred in three stages: the Great Oxygenation Event 2.4 to 2.0 billion years ago, a second increase between 800 and 500 million years ago, and a third increase between 450 and 250 million years ago. The Earth's atmosphere was not always rich in oxygen, and it took billions of years for the atmosphere to evolve into its current state.

Subduction and Oxygen Levels

The research team suggests that changes in subduction may have influenced atmospheric oxygen by controlling how much carbon and sulfur were carried into the deep interior of the Earth. When the mantle is hotter, carbon and sulfur are released into the shallow mantle and can scavenge oxygen molecules in the atmosphere. In contrast, a cooler mantle allows more carbon and sulfur to be carried deeper into the Earth, reducing the amount available to scavenge oxygen.

Geological Evidence

The team compiled a broad picture of the history of subduction by analyzing minerals and chemistry in rocks that have been subducted and then returned to the surface. The data shows that lower-temperature subduction occurred between 2.2 and 1.8 billion years ago and again for the last 800 million years, aligning with the increases in oxygen levels. The researchers also found that the assembly and breakup of supercontinents, such as Columbia, Gondwana, and Pangaea, played a role in the oxygenation of the atmosphere.

Key points

• The oxygenation of Earth's atmosphere occurred in three stages: 2.4-2.0 billion years ago, 800-500 million years ago, and 450-250 million years ago.
• Changes in subduction may have influenced atmospheric oxygen by controlling carbon and sulfur levels.
• Lower-temperature subduction allows more carbon and sulfur to be carried deeper into the Earth, reducing oxygen scavenging.
• The assembly and breakup of supercontinents, such as Columbia, Gondwana, and Pangaea, played a role in oxygenation.
• The research team used geological evidence to compile a history of subduction and its impact on oxygen levels.
• The study suggests that the net flux of carbon and sulfur between Earth's interior and exterior controlled the oxygen balance.