Archives par mot-clé : Oxygen

Billion-year-old lake deposit yields clues to Earth’s ancient biosphere

by McGill University, July 18, 2018 in ScienceDaily


The findings, published in the journal Nature, represent the oldest measurement of atmospheric oxygen isotopes by nearly a billion years. The results support previous research suggesting that oxygen levels in the air during this time in Earth history were a tiny fraction of what they are today due to a much less productive biosphere.

“It has been suggested for many decades now that the composition of the atmosphere has significantly varied through time,” says Peter Crockford, who led the study as a PhD student at McGill University. “We provide unambiguous evidence that it was indeed much different 1.4 billion years ago.”

The study provides the oldest gauge yet of what earth scientists refer to as “primary production,” in which micro-organisms at the base of the food chain — algae, cyanobacteria, and the like — produce organic matter from carbon dioxide and pour oxygen into the air.

Volcanic activity, declining ocean oxygen triggered mass extinction of ancient organisms

by Florida State University, June 11, 2018 in ScienceDaily


Global climate change, fueled by skyrocketing levels of atmospheric carbon dioxide, is siphoning oxygen from today’s oceans at an alarming pace — so fast that scientists aren’t entirely sure how the planet will respond.

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Millions of years ago, scientists discovered, powerful volcanoes pumped Earth’s atmosphere full of carbon dioxide, draining the oceans of oxygen and driving a mass extinction of marine organisms.