A new tool for eruption forecasting
With its 78% nitrogen and 21% oxygen, the Earth's atmosphere is a unique mixture in the Solar System - on Venus and Mars, the atmosphere is essentially composed of carbon dioxide. Oxygen was produced by some of the first living organisms, but where did the nitrogen come from? Did it escape from the Earth's mantle through volcanism?
Publication date: 16/04/2020
Press, Research
Related teams :
Stable Isotope Geochemistry
Related themes : Natural Hazards
To try and answer these questions, Jabrane Labidi, a CNRS researcher at the Institut de Physique du Globe de Paris (CNRS/IPGP/IGN/Université de Paris)1 and his colleagues took gas samples from various volcanic sites on Earth. They have shown that the nitrogen coming from magmas formed in the mantle does not have the same isotopic composition2 as that in the atmosphere: it does not therefore come from the degassing of the mantle, according to their study published on 16 April 2020 in the journal Nature. However, these measurements enabled the team to distinguish, in the geysers, fumaroles and other gaseous manifestations of volcanoes, between the contribution of the atmosphere (in the form of heated rainwater) and that of the Earth’s mantle (magmatic gases): small quantities of magmatic gases were detected in the Yellowstone geysers, a sign of renewed activity.
These precision measurements could therefore help to predict the awakening of volcanoes. Samples are still being taken at Yellowstone, and others will be taken in the fumaroles of the Mayotte islands, off the coast of which a new undersea volcano has recently erupted. As for the origin of atmospheric nitrogen, it remains a mystery… for now.
Notes :
1 – Previously at the University of California at Los Angeles (UCLA). In addition to the Institut de physique du globe de Paris (CNRS/IPGP/IGN/Université de Paris), this work involved the Centre de recherches pétrographiques et géochimiques (CNRS/Université de Lorraine) in France.
2 – A chemical element can exist in different versions, called isotopes, which are distinguished by their mass. For example, three isotopic variants of dinitrogen exist in nature: 14N14N, 14N15N and, more rarely, 15N15N. It is the abundance of the latter that has made it possible to distinguish between mantle and atmospheric origins.
Ref:
Hydrothermal 15N15N abundances constrain the origins of mantle nitrogen, J. Labidi, P.H. Barry, D.V. Bekaert, M.W. Broadley, B. Marty, T. Giunta, O. Warr, B. Sherwood Lollar, T.P. Fischer, G. Avice, A. Caracausi, C.J. Ballentine, S.A. Halldórsson, A. Stefánsson, M. D. Kurz, I.E. Kohl, E. D. Young. Nature, 16 avril 2020. DOI : 10.1038/s41586-020-2173-4
