New Oxygen research; new theory of abundance (Introduction)

by David Turell , Sunday, January 01, 2017, 01:05 (2674 days ago) @ David Turell
edited by David Turell, Sunday, January 01, 2017, 01:12

This theory involves the burial of organic materials like coal and oil causing the increase in atmospheric oxygen. Perhaps more important than just the production of oxygen by photosynthesis:

https://www.sciencedaily.com/releases/2016/12/161230185406.htm

"Oxygen enables the chemical reactions that animals use to get energy from stored carbohydrates -- from food. So it may be no coincidence that animals appeared and evolved during the "Cambrian explosion," which coincided with a spike in atmospheric oxygen roughly 500 million years ago.

"It was during the Cambrian explosion that most of the current animal designs appeared.

"In green plants, photosynthesis separates carbon dioxide into molecular oxygen (which is released to the atmosphere), and carbon (which is stored in carbohydrates).

"But photosynthesis had already been around for at least 2.5 billion years. So what accounted for the sudden spike in oxygen during the Cambrian?

"A study now online in the February issue of Earth and Planetary Science Letters links the rise in oxygen to a rapid increase in the burial of sediment containing large amounts of carbon-rich organic matter. The key, says study co-author Shanan Peters, a professor of geoscience at the University of Wisconsin-Madison, is to recognize that sediment storage blocks the oxidation of carbon.

"Without burial, this oxidation reaction causes dead plant material on Earth's surface to burn. That causes the carbon it contains, which originated in the atmosphere, to bond with oxygen to form carbon dioxide. And for oxygen to build up in our atmosphere, plant organic matter must be protected from oxidation.

"And that's exactly what happens when organic matter -- the raw material of coal, oil and natural gas -- is buried through geologic processes.

***

"our argument is that there are mechanistic connections between geology and the history of atmospheric oxygen," Husson says. "When you store sediment, it contains organic matter that was formed by photosynthesis, which converted carbon dioxide into biomass and released oxygen into the atmosphere. Burial removes the carbon from Earth's surface, preventing it from bonding molecular oxygen pulled from the atmosphere."

"Some of the surges in sediment burial that Husson and Peters identified coincided with the formation of vast fields of fossil fuel that are still mined today, including the oil-rich Permian Basin in Texas and the Pennsylvania coal fields of Appalachia.

"'Burying the sediments that became fossil fuels was the key to advanced animal life on Earth," Peters says, noting that multicellular life is largely a creation of the Cambrian.

***

"The ultimate geological cause for the accelerated sediment storage that promoted the two surges in oxygen remains murky. "There are many ideas to explain the different phases of oxygen concentration," Husson concedes. "We suspect that deep-rooted changes in the movement of tectonic plates or conduction of heat or circulation in the mantle may be in play, but we don't have an explanation at this point."

"Holding a chunk of trilobite-studded Ordovician shale that formed approximately 450 million years ago, Peters asks, "Why is there oxygen in the atmosphere? The high school explanation is 'photosynthesis.' But we've known for a long time, going all the way back to Wisconsin geologist (and University of Wisconsin president) Thomas Chrowder Chamberlin, that building up oxygen requires the formation of rocks like this black shale, which can be rich enough in carbon to actually burn. The organic carbon in this shale was fixed from the atmosphere by photosynthesis, and its burial and preservation in this rock liberated molecular oxygen."

"What's new in the current study, Husson says, is the ability to document this relationship in a broad database that covers 20 percent of Earth's land surface.
Continual burial of carbon is needed to keep the atmosphere pumped up with oxygen.

" Many pathways on Earth's surface, Husson notes, like oxidation of iron -- rust -- consume free oxygen. "The secret to having oxygen in the atmosphere is to remove a tiny portion of the present biomass and sequester it in sedimentary deposits. That's what happened when fossil fuels were deposited."

Comment: A fascinating theory. Oxygen is stored in the atmosphere only when carbon is sequestered. Certainly the oxygen levels rose before the Cambrian and burial of Earth's layers is caused by subduction of continental plate edges, and, of course, volcanism. Lava layers and shale layers can be and are above and below each other. This is a reminder that the Earth is a special planet with a liquid iron/nickel core creating a magnetic field which is very protective of the life that appeared by blocking nearly all the nasty radiation that abounds in the universe. Humans appeared only after a very long evolutionary process of stages, starting with a sterile Earth, modified by simple early life which then prepares a different Earth for the arrival of complex life in the Cambrian. Not by chance!