Carbon dioxide emission to Earth’s surface by deep-sea volcanism

Large amounts of CO 2 are transferred from Earth’s interior to the surface by volcanism. On a geological time scale, the rate of CO 2 emission has controlled the evolution of Earth’s atmosphere and climate, as well as the dynamic processes that take place in the mantle and core. The total rate of natural CO 2 emission from Earth has been estimated on the basis of CO 2 fl ux from arc, mid-ocean-ridge, and hotspot volcanism. However, previous estimates have overlooked the CO 2 emitted from a recently discovered type of volcanism—petit-spot volcanism—that occurs on the deep-sea fl oor. Here, we measure the CO 2 and H 2 O contents of glassy basalts produced by petit-spot volcanism and estimate the initial contents to be >5 wt% and 1.0–1.1 wt%, respectively. Based on these values and magma fl ux of petitspot volcanism, we show that the rate of CO 2 emission from petitspot volcanoes (2.7–5.4 × 10 11 g CO 2 yr –1 ) is a few percent of the CO 2 emissions from arc and mid-ocean-ridge volcanism, and up to ~14% of that from hotspot volcanism. Thus, the contribution to the carbon cycle on Earth of the large amounts of CO 2 that have been emitted from the deep-sea fl oor by petit-spot volcanism has not previously been recognized.