Annual Volcanic Carbon Dioxide Emission: 
An Estimate from Eruption Chronologies 
Laboratory of Isotope Geochemistry 
Department of Geosciences 
University of Arizona 
Tucson, Arizona 85721 
ABSTRACT [ Continuing interest in the effects of carbon dioxide on climate has been promoted by the exponentially increasing 
anthropogenic production of COz. Volcanoes are also a major source of carbon dioxide, but their average input to the at- 
mosphere is generally considered minor relative to anthtopogenic input. ]his study examines eruption chronologies to 
determine a new estimate of the volcanic CO 2 input and to test if temp(~ral fluctuations may be resolved. Employing represen- 
tative average values of 2.7 g cm-a as density ot erupted material, 0.2 wt percent C02 in the original melt, 60 percent
degassing during eruption, and an average volume of 0.1 km ^3 for each of the eruptions in the recently published eruption 
chronology of Hirschboeck (1980), a volcanic input of about 1.5 * 10^11 moles CO 2 yr- 1 was determined for the period 1800- 
1969. The period 1800-1899 had a somewhat lower input than 1900~1969, which could well be related more to completeness of 
observational data than to a real increase in volcanic CO2. This input is well below man's current CO 2 production of 
4-5 -10^14 moles C02Yr -1. The average values above together with specific volumetric 
estimates were employed to calculate CO 2 input from individual historic eruptions, massive flood basalts, and ash-llow eruptions. 
Total CO 2 release from the largest of flood basalt and ash-flow sequences was 10^15--10^16 moles of CO 2. The impact of these 
sources on global atmospheric CO 2 and climate, however, will be limited by the duration and spacing of the major individual 
eruptive periods in the sequences.



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