Fool's gold is the colloquial name for pyrite, a frequently occurring mineral that forms golden cubes as a crystal but has a black color when finely distributed in ocean sediments.
Fool's gold is the colloquial name for pyrite, a frequently occurring mineral that forms golden cubes as a crystal but has a black color when finely distributed in ocean sediments. On exposure to the air pyrite is oxidized and produces an acid, which in turn dissolves carbonate minerals and releases the greenhouse gas carbon dioxide (CO2) into the atmosphere. Martin Kölling of MARUM has studied the consequences of pyrite weathering in the context of the sea-level changes that are associated with glacial cycles. His calculations are based on the basic fact that during glacials, sea level was more than 100 meters lower than it is today. With sea levels that low, more than 20 million square kilometers of present-day shelf were exposed to atmospheric oxygen, which resulted in large-scale pyrite weathering and release of CO2 into the atmosphere.
Compared to today's man-made release of CO2, the pyrite-driven glacial release was a small but significant amount, on the same order of magnitude as volcanic CO2 emissions. "Globally, this is an amount large enough to affect the climate system," says Kölling. Especially since those CO2 emissions systematically occurred before the end of glacial periods. "Based on our calculations, we suspect that this process helped to end the glacials. Pyrite weathering could be a hitherto neglected process that indirectly controls the melting of glaciers through the greenhouse effect and thus enables rapid sea-level rise that marks the end of a glacial period.
For the model, Kölling has analyzed and compared published CO2 levels and sea-level reconstructions covering the past 800,000 years. Except for phases of very low sea level during glacials, Kölling and his colleagues found that sea level and carbon dioxide correlate surprisingly well: If sea level rises by one meter, the CO2 content increases by 0.001 per mille. Over the past 800,000 years, sea levels have been closely linked to carbon dioxide levels.
Read more at MARUM – Center for Marine Environmental Sciences
Photo Credit: Riotinto2006, CC0
