A new study led by the University of Oxford has overturned the view that natural rock weathering acts as a CO2 sink, indicating instead that this can also act as a large CO2 source, rivaling that of volcanoes.
For the first time this new study measured an additional natural process of CO2 release from rocks to the atmosphere, finding that it is as significant as the CO2 released from volcanoes around the world.
Shale rocks high up in the remote Mackenzie mountains Canada, which contain lots of rock organic carbon and are hotspots of CO2 release.
Landslides in the high Andes of Peru, exposing rocks full of organic matter to weathering which can release CO2.
The global CO2 release from rock organic carbon weathering was found to be 68 megatons of carbon per year.
Professor Robert Hilton, who leads the ROC-CO2 research project that supported the study, said, "This is about 100 times less than present day human CO2 emissions by burning fossil fuels, but it is similar to how much CO2 is released by volcanoes around the world, meaning it is a key player in Earth's natural carbon cycle." These fluxes could have changed during Earth's past.
High erosion in southern France exposes these sedimentary rocks to weathering, releasing CO2 as the ancient organic carbon breaks down.
https://phys.org/news/2023-10-ancient-carbon-dioxide-world-volcanoes.html
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